Sulfonate-tagged 1,4-diazabutadiene (DADS) ligands and their noble-metal complexes - Synthesis, characterization and immobilization in ionic liquids

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Sulfonate-tagged 1,4-diazabutadiene (DAD^S) ligands and their noble-metal

complexes – synthesis, characterization and immobilization in ionic liquids†

Benjamin Oelkers and Jo¨rg Sundermeyer*

Received 18th May 2011, Accepted 2nd September 2011

DOI: 10.1039/c1dt10939a

A series of sulfonate-tagged 1,4-diazabutadiene (DAD^S) ligands was prepared as salts with typical ionic

liquid (IL) cations ([EMIM]⁺, [BMIM]⁺, [BMMIM]⁺, Bu₄N⁺, Bu₃PMe⁺, [Gua-4,4-4,4-4,1]⁺).

Complexation behaviour of the ligands was investigated by preparing complexes of the types

[BMMIM]₂[MCl₂(DAD^S)] (M = Pd, Pt), [BMMIM][Rh(COD)(DAD^S)] and [BMMIM]₂[Mo(CO)₄-

(DAD^S)]. Using UV-Vis spectroscopy, the latter sulfonate-tagged chromophore was shown to be well

soluble in the sulfonate IL [BMIM]OTf and completely insoluble in toluene, resulting in perfect

immobilization. The crystal structures of [HNEt₃]₂[2,6-Me₂-Me-DAD^S], [BMIM]₂[2,6-Me₂-Me-DAD^S],

[BMMIM]₂[2,4,6-Me₃-Me-DAD^S], [BMMIM]₂[2,6-iPr₂-Me-DAD^S] and [HNEt₃]₂[PdCl₂(2,6-Me₂-Me-

DAD^S)] were determined. Regarding the diimine fragment, they show geometries similar to the

respective non-sulfonated parent compounds.

that the sodium salts of these modiﬁed ligands can be used to

stabilize active palladium species in the aerobic alcohol oxidation

Introduction

and in the Suzuki coupling under aqueous conditions.¹¹One

tetrabutylammonium salt and two [BMIM]⁺salts were also

prepared using salt metathesis protocols. However, such ligands

and the corresponding complexes often show slow degradation in

water-based applications due to hydrolysis of the diimine moiety.¹²

The potential stability beneﬁt of non-aqueous, IL-based azaligand

catalyst systems has not been exploited so far. Plenio and co-

workers presented similar DAD^Ssodium salts as intermediates

in the synthesis of water-soluble N-heterocyclic carbenes. These

were applied as ligands for palladium-catalyzed Suzuki coupling

in water.¹³

Regarding the choice of anionic tags, sulfonates are used most

often as they show a range of favourable characteristics, i.e.

relatively low nucleophilicity, thermal stability under aprotic as

well as aqueous conditions, good stability towards oxidation and

reduction. Salts of sulfonate-tagged ligands bearing sodium or

similar inorganic cations usually show sufﬁcient solubility in ILs

to serve as catalysts. Nevertheless, the preparation of salts bearing

IL-typical onium cations (e.g. alkyl substituted imidazolium,

ammonium, phosphonium) seems worthwhile because they most

likely prevent problems concerning low solubility, increasing

viscosity due to ion pairing effects or side reactions associated

with “foreign” ions. We present here a general approach towards

DAD^Sligands with various onium cations via acid–base reactions

and towards their noble-metal complexes. The solubility and

immobilization of such complexes in ILs is quantitatively shown

via photometric measurements using a chromophoric Mo(0)

DAD^Scomplex in a toluene/[BMIM]OTf biphasic mixture as

model system.

Ionic liquids (ILs) are most promising media for multiphasic

catalysis.¹They offer high polarity that is often needed to

stabilize reactive intermediates in combination with an aprotic

environment as required in many organometallic transformations.

Consequently, it is possible to combine advantages of multiphasic

aqueous catalysis with the unique “designer-solvent” properties

of ILs.²Among the criteria for transition-metal complexes to be

applied as catalysts in multiphasic IL-based processes, selective

solubility in the IL is one of the most important ones. Only

if the catalyst is completely immobilized in the IL by some

means it can be retained efﬁciently and thus be recycled easily.³

Learning again from aqueous biphasic catalyst systems,⁴the

modiﬁcation of the ligand periphery with ionic substituents such

as imidazolium⁵or sulfonate groups⁶has been used successfully

for the immobilization of phosphorous and bipyridine ligands and

their transition-metal complexes in ILs.⁷

While some work has been done concerning the immobiliza-

tion of phosphanes using cationic or anionic tags, much less

is known about immobilization of azaligand complexes with

anionic tags in ionic liquids. Sulfonate-tagged derivatives of

bipyridine,⁸phenanthroline⁹and pyridylimine¹⁰are well known,

but have mainly been applied as sodium salts for aqueous

catalysis. Concerning sulfonated 1,4-diazadiene (DAD^S) ligands,

three studies have been published. Sun and co-workers showed

Philipps-Universita¨t Marburg, Fachbereich Chemie, Hans-Meerwein-

Straße, 35032, Marburg, Germany. E-mail: jsu@staff.uni-marburg.de;

Fax: +49 (0)6421 28-25711; Tel: +49 (0)6421 28-25693

† CCDC reference numbers 826519–826523. For crystallographic data in

CIF or other electronic format see DOI: 10.1039/c1dt10939a

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Results and discussion

Ligand synthesis

The preparation of triethylammonium salts 4a–c of sulfonate-

tagged 1,4-diazabutadiene (DAD^S) ligands is outlined in Scheme 1.

Commercially available alkylated anilines 1a–c were transformed

into the corresponding sulfanilic acids 2a–c by sulfonation accord-

ing to known procedures.¹⁴After preparation of the corresponding

triethylammonium salts 3a–c the desired DAD^Sligands were

obtained by condensation with butane-2,3-dione in methanol. All

studied DAD^Sligands were obtained as yellow solids.

Scheme 2 Cation exchange with basic cation precursors.

Synthesis of complexes

Scheme 1 Synthesis of DAD^Sligands.

While it has been shown that the disodium salts of DAD^S

ligands can be used to introduce the desired onium-cations via

salt metathesis,¹¹we discarded this method because it needs

accurately tuned reaction conditions for each ligand and cation to

be introduced, otherwise complicated salt mixtures are obtained.

The reason for these problems was found to be the very polar

and hydrophilic nature of the doubly charged DAD^Sanions. In

order to completely avoid contamination of the products with

halide and alkali metal ions, acid–base reactions were chosen

instead of salt metathesis as the key step of the ligand synthesis. A

number of basic cation precursors that are also used in high-purity

syntheses of ILs themselves was utilized for the transformation of

the triethylammonium salts 4a–c as shown in Scheme 2.

In all cases, the desired onium-salts 5–11 were obtained in

high yield and purity upon reaction of the appropriate HNEt₃

salt with two equivalents of the respective cation precursor in

acetonitrile. For the highly reactive and (partly) temperature-

sensitive N-heterocyclic carbenes,¹⁵N,N-ketenediacetals¹⁶and

P-ylides,¹⁷the reactions were carried out at -40 ^◦C, while

the ammonium hydroxides, imidazolium methylcarbonates and

guanidinium methylcarbonates¹⁸were used at room temperature.

Triethylamine is released as byproduct of the reaction and can

easily be removed in vacuo. All other byproducts (if any) are

volatile as well and no contamination of the ligand salts with

“simple” inorganic ions such as alkali metal or halide ions is

possible, thus eliminating this often most difﬁcult issue arising

from salt metathesis protocols.

To demonstrate the potential scope of applications, a number

of prominent noble-metal complexes were synthesized start-

ing from the [BMMIM]₂[DAD^S] ligands 8a–c. The 1-butyl-

2,3-dimethylimidazolium cation ([BMMIM]⁺) was chosen in-

stead of the more common 1-butyl-3-methylimidazolium cation

([BMIM]⁺) because the latter is known to easily form carbene com-

plexes, especially in combination with palladium(II) precursors.¹⁹

Furthermore, molybdenum tetracarbonyl complexes were chosen

to probe the immobilization concept via UV-Vis spectroscopy.

Palladium dichloro complexes. Palladium complexes of aza-

ligands are most versatile catalysts for a variety of im-

portant synthetic transformations.^20–23Examples that have

been shown for DAD ligand-based systems are oleﬁn

polymerization,²²CO/styrene copolymerization,²³cyclooligomer-

ization of alkynes,²⁴C(sp²)–C(sp²) bond formation^11,25and aerobic

alcohol oxidation.¹¹Hence we decided to investigate whether

the coordination behaviour of the DAD^Sligands is considerably

different from that of the well-known DAD ligands by synthesizing

the corresponding dichloro complexes (Scheme 3).

Similar to known procedures,²⁶the complexes 12a–d are

obtained in high yield upon reaction of [PdCl₂(MeCN)₂] or

[PdCl₂(PhCN)₂] with the appropriate ligand at room temperature.

Acetonitrile proved useful as solvent for this as well as most of the

other complexation reactions. It combines sufﬁcient polarity to

(partly) dissolve the salt-like ligands and complexes with inertness

towards most reactions catalyzed by the formed complexes.

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incorporated into an anion due to the doubly charged DAD^S

ligand system. The participation of ions not belonging to the

ﬁnal product cannot be avoided in this case. The complexa-

tion was achieved using [Rh(COD)(MeCN)₂]BF₄, prepared in

situ from [{Rh(COD)Cl}₂] and AgBF₄in acetonitrile at room

temperature (Scheme 5). Therefore, the stoichiometric byproduct

was [BMMIM]BF₄, which could be separated from the less

lipophilic complexes 14a–c by washing the product mixture with

dichloromethane–ether (1 : 1).

Scheme 3 Synthesis of complexes of the type [BMMIM]₂[PdCl₂(DAD^S)]

(12a–c) and [HNEt₃]₂[PdCl₂(2,6-Me₂-Me-DAD^S)] (12d).

Platinum dichloro complexes. Platinum(II) complexes of DAD

ligands are of growing interest as they are known to activate C–H

bonds.^27,28As they are much more inert towards ligand substitution

than their palladium analogues, formation of the DAD^Sdichloro

complexes 13a–c was investigated as an example of more subtle

choice of metal source (Scheme 4).

Scheme

5 Synthesis of complexes of the type [BMMIM]-

[Rh(COD)(DAD^S)] (14a–c).

Scheme 4 Reactivity of DAD^Sligands 8 towards different PtCl₂synthons.

Molybdenum tetracarbonyl complexes. Molybdenum carbonyl

complexes with DAD ligands are well-known and have been

extensively studied, mainly in terms of their optical properties.³⁴

For the evaluation of the immobilization concept, both a

complex with a “classical”, non-sulfonated DAD ligand (15) and

its counterpart incorporating a DAD^Sligand (16) were prepared

by heating the free ligand with Mo(CO)₆in a suitable solvent, i.e.

toluene and 1,2-dichloroethane, respectively (Scheme 6).

In order to avoid side reactions, all attempts to prepare the

complexes [BMMIM]₂[PtCl₂(DAD^S)] (13a–c) were conducted at

room temperature. The simplest possible precursor for the desired

platinum dichloro complexes, PtCl₂, was found to react rather

slowly with a solution of the appropriate ligand 8, presumably

because of its hexameric nature.²⁹The better soluble nitrile

adducts [PtCl₂(MeCN)₂] and [PtCl₂(PhCN)₂] were completely

unreactive towards ligand substitution in acetonitrile solution,

thus showing a distinctive difference in reactivity compared to the

corresponding palladium precursors (vide supra). [PtCl₂(COD)]

and [PtCl₂(SMe₂)₂] are reported to show little reactivity in similar

complex formations with DAD ligands^27,30and were not tested.

In contrast to that, Zeise’s salt, K[PtCl₃(C₂H₄)]·H₂O, is known

as labile precursor for dichloro complexes.^27,31However, it was

dismissed in this case because it inevitably introduces further ions

into the reaction mixture. This, in turn, is likely to cause problems

such as contamination of the product with foreign ions or even

complete formation of an undesired salt due to solubility effects.

Alternatively, Zeise’s dimer, [{PtCl₂(C₂H₄)}₂], was chosen as labile

starting material.²⁷The desired complexes 13a–c were formed in

high yields by reaction of this platinum source with the appropriate

ligand in methanol at room temperature. Stirring was continued

for three days to assure complete reaction (Scheme 4); however,

much shorter reaction times are sufﬁcient when gentle heating is

applied.

Scheme 6 Synthesis of molybdenum tetracarbonyl complexes.

Rhodium cyclooctadiene complexes. Rhodium(I) complexes of

azaligands are well-known as catalysts for (asymmetric) trans-

fer hydrogenation³²and hydrosilylation³³of ketones. We chose

rhodium(I) DAD^Scyclooctadiene complexes [Rh(DAD^S)(COD)]^-

as an example of a formally monocationic metal centre that is

Spectroscopic properties

NMR spectroscopy. The H and ¹³C NMR spectra of both

the free ligands (4–11) and the various complexes (12–14, 16) in

DMSO-d₆or CD₃CN show the typical signals belonging to the

1

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Table 1 Comparison of ¹H and ¹³C NMR shifts (d (ppm), DMSO-d₆, 298 K) for DAD and DAD^Sligands

N

CCH₃

N

CCH₃

N

CCH₃C_ipso

C_orthoCH₃

C_orthoCH₃CH(CH₃)₂CH(CH₃)₂C_paraCH₃C_paraCH₃

(2,6-Me₂-Me-DAD)

167.6

167.9

167.6

15.5

15.6

16.3

15.6

15.5

1.95

1.93

1.98

1.96

1.90

148.0 17.3

1.96

1.92

2.66^a

1.97

—

20.3

—

22.7

—

2.23

—

2.50

(2,4,6-Me₃-Me-DAD)

(2,6-iPr₂-Me-DAD)

145.6 17.3

145.6 28.0^a

147.9 17.3

1.09/1.15^b22.4/22.8^b

[BMMIM]₂[2,6-Me₂-Me-DAD^S]

—

[BMMIM]₂[2,4,6-Me₃-Me-DAD^S] 167.7

146.6 15.8/15.9^b2.22/2.23^b

17.2/17.3^b1.87/1.89^b

[BMMIM]₂[2,6-iPr₂-Me-DAD^S]

168.0

16.3

1.99

145.7 28.0^a

2.66^a

1.09/1.15^b22.3/22.7^b

—

^aValues correspond to CH(CH₃)₂and CH(CH₃)₂, respectively. ^bTwo rotamers are observed.

respective cation. The anions seem to have little inﬂuence on the

cations’ signals and vice versa. This behaviour indicates a truly

ionic nature of the investigated substances; no extensive ion pairing

effects were observed in any of the NMR spectra.

for the imine carbon signal. While the rhodium(I) COD complexes

14a–c show an almost identical downﬁeld shift, the platinum(II)

dichloro complexes 13a–c exhibit a slightly smaller deshielding of

the imine carbon atoms (12–13 ppm).

The NMR signals corresponding to the respective anion of the

free DAD^Sligands are rather similar to those obtained for the

classical, non-sulfonated DAD ligands concerning all resonances

that are not directly affected by the differing aromatic substitution

patterns (Table 1). Resonances of the diimine backbone are found

at around 168 ppm in DMSO-d₆for all three ligands 8a, 8b and

8c. A single imine signal is present in all cases for both the free

ligands and metal complexes presented herein. The ligands and

complexes carrying isopropyl substituents invariably show two

signals for the corresponding methyl groups due to restricted

rotation of the iPr groups. In contrast to that, two sets of signals

belonging to the aromatic ortho-methyl groups are observed

only for the mesitylamine-derived free ligands (4b and 8b) and

the rhodium(I) complex 14b but not for the palladium(II) and

platinum(II) complexes (12b and 13b). This ﬁnding can presumably

be attributed to syn/anti isomerism regarding the orientation of

the sulfonate groups (vide infra).

Although the free ligands’ NMR spectra do not show signif-

icant differences compared to their non-sulfonate tagged parent

compounds in the case of para-sulfonated aromatics (Table 1), an

electron-withdrawing effect especially of the para-sulfonate groups

on the diimine fragment has to be expected. It has been shown for

a series of aromatic DAD ligands bearing different substituents in

the para-position that the electronic environment of coordinated

palladium is clearly affected by the aromatic substitution pattern

while there is little difference in the NMR spectra of the free

ligands.³⁵

Comparison of the ¹⁹⁵Pt NMR signals of the complexes 13a–c

with known values³⁰shows that the electronic inﬂuence of the aryl

groups’ substitution is by far less pronounced than that of the

diimine backbone (Table 2). Electron-withdrawing substituents at

the imine carbons cause a greater p-acidity of the ligand and thus

a less electron-rich metal centre. Regarding the aryl substitution

pattern, no clear trend is found. The overall electronic situation

at the metal centre seems to be more affected by the bulkiness

of the aromatic substituents than by the presence or absence of

para-sulfonate groups.

The rhodium(I) COD complexes 14a and 14c show three broad

1

signals of equal intensity in the H NMR spectra belonging to

the two diastereotopic sets of methylene protons and the four

equivalent oleﬁnic protons. For the mesitylamine-derived complex

14b two signals for the oleﬁnic protons are observed, showing the

two inequivalent faces of the metal–ligand plane caused by the

non-symmetric substitution of the aromatic ring (Scheme 7). In

the case of 14a and 14c, the ¹³C NMR spectra show two signals for

the COD ligand, of which the oleﬁnic resonance at around 89 ppm

features a ¹J_RhCcoupling constant of about 11–12 Hz that is also

observed for similar rhodium COD complexes.³⁶In the case of

14b, two sets of these signals could be identiﬁed due to the above-

mentioned reason. However, additional splitting of the signals is

expected in the case of syn/anti isomers (Scheme 7), which could

not be clearly resolved from the obtained NMR spectra.

Mass spectrometry. All ligands and complexes were character-

ized by high-resolution electrospray ionization-mass spectrometry

(HR ESI-MS) using acetonitrile as solvent. The cations of the

Upon complexation of the Lewis-acidic fragment PdCl₂, a

signiﬁcant downﬁeld shift of approximately 14 ppm is observed

Table 2 ¹⁹⁵Pt NMR shifts (d (ppm), DMSO-d₆, 298 K) for complexes of the types [PtCl₂(DAD)] and [PtCl₂(DAD^S)]^2-

Substituents at

Aryl

Diimine

¹⁹⁵Pt (d (ppm))

[PtCl₂(2,6-Me₂-CF₃-DAD)]

[PtCl₂(2,6-Me₂-H-DAD)]

2,6-Me₂

2,6-Me₂, 4-SO₃

2,4,6-Me₃, 3-SO₃

2,6-iPr₂, 4-SO₃

CF₃

H

Me

-1183^a

-2100^a

-2179^a

-2193

-2192

-2169

[PtCl₂(2,6-Me₂-Me-DAD)]

[BMMIM]₂[PtCl₂(2,6-Me₂-Me-DAD^S)] (13a)

[BMMIM]₂[PtCl₂(2,4,6-Me₃-Me-DAD^S)] (13b)

[BMMIM]₂[PtCl₂(2,6-iPr₂-Me-DAD^S)] (13c)

-

^aRef. 30.

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Fig. 1 Molecular structure of 4a. Displacement ellipsoids are shown for

50% probability, carbon-bound hydrogen atoms are omitted for clarity.

Symmetry-equivalent atoms are generated by ¢ = -x, -y, 1 - z.

Scheme 7 Possible conformers of 14b. While the syn conformer has C_s

symmetry, the anti conformer shows C₂symmetry. Both conformers have

two different a and b positions; up to four sets of COD signals can be

distinguished in total.

respective salts were identiﬁed in positive ionization mode while

the anions were observed in negative ionization mode. In the case

of doubly charged anions the dominating mass peak was attributed

to [anion]^2-. Apart from this anion peak, small clusters of the form

[anion + cation]^-were found with medium to low intensity in some

cases.

Crystal structures

Fig. 2 Molecular structure of 6. Displacement ellipsoids are shown for

50% probability, hydrogen atoms are omitted for clarity. Symmetry-equiv-

alent atoms are generated by ¢ = 2 - x, -y, -z.

Single-crystal analyses could be obtained for four salts of the free

ligands, covering all three different DAD^Sanions, as well as for

the palladium complex 12d (Fig. 1–5). Selected bond lengths and

angles are shown in Table 3 and in the legend of Fig. 5, respectively.

Full details are available in ESI†.

All four crystal structures of the free DAD^Sligands have an

asymmetric unit that contains only half a formula unit. The

anions are each completed by an inversion centre in the middle of

the central carbon–carbon bond (C101–C101¢). Because of that,

the planar diimine moieties of the DAD^Sligands show perfect

anti conformation. They are not coplanar with the aromatic

substituents but show torsion angles of 82–90^◦. All bond lengths

are in the expected ranges of single and double bonds, respectively

(Table 3). The overall geometry of the anions is thus quite similar

Fig. 3 Molecular structure of 8b. Displacement ellipsoids are shown for

50% probability, hydrogen atoms are omitted for clarity. Symmetry-equiv-

alent atoms are generated by ¢ = 1 - x, -y, 2 - z.

Table 3 Selected bond lengths (pm) and angles (^◦) of the DAD^Sligands.

Symmetry operations for equivalent atoms are given at Fig. 1–4

4a

6

8b

8c

C101–N101

C101–C101¢

C101–C102

N101–C103

126.3(3) 127.4(2) 127.1(2)

150.3(4) 150.0(3) 149.2(4)

149.3(3) 149.2(3) 149.8(3)

143.2(3) 142.5(2) 142.7(2)

122.8(5)

149.7(7)

152.9(7)

144.6(4)

C101–N101–C103

N101–C101–C101¢

N101–C101–C102

C102–C101–C101¢

121.3(2) 120.1(2) 120.9(2)

116.6(3) 116.4(2) 116.6(2)

125.9(2) 126.0(2) 125.7(2)

117.5(3) 117.6(2) 117.7(2)

122.2(4)

120.4(6)

125.7(4)

113.9(5)

180^a

Fig. 4 Molecular structure of 8c. Displacement ellipsoids are shown for

50% probability, hydrogen atoms are omitted for clarity. Symmetry-equiv-

alent atoms are generated by ¢ = 2 - x, -y, -z.

N101–C101–C101¢–N101¢ 180^a

180^a

C102–C101–C101¢–C102¢

C101–N101–C103–C104

C101–N101–C103–C108

180^a

87.8(2)

95.7(2)

180^a

to that of non-sulfonated DAD ligands^37,38and of [BMIM]₂[2,6-

Et₂-Me-DAD^S].¹¹

84.7(3) 90.2(2)

101.4(3) 95.8(2)

82.2(6)

108.8(5)

The palladium dichloro complex 12d shows an essentially

square-planar coordination geometry with an acute N–Pd–N

^aRestricted due to crystal symmetry.

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Immobilization in ILs

The effectiveness of immobilization of the herein described

complexes was tested using UV-Vis spectroscopy. As the sol-

vatochromic molybdenum tetracarbonyl complexes 15 and 16

give rise to intensely purple coloured solutions due to MLCT

transitions,³⁴solubility and phase distribution behaviour can easily

be monitored. Another interesting feature of the chosen complexes

is their rather unpolar metal environment, rendering leaching out

of the highly polar IL phase facile in the case of non-immobilizing

ligands.

Solutions of the solvatochromic complexes 15 and 16 in

[BMIM]OTf both showed the same absorption maximum of

525 nm. Combined with their quite similar high-energy CO

stretching modes (1993 and 1996 cm^-1, respectively) and the nearly

identical carbon NMR shifts of the carbonyl ligands this is a strong

indication that the electronic inﬂuence of the additional sulfonate

groups towards the metal centre is neglectable at least in this case.

The saturation limit of the immobilized complex 16 was found

to be considerably higher for the IL than that of the “classical”

complex 15 without sulfonate tags (Table 4). As shown in Fig. 7,

the molybdenum tetracarbonyl complex 15 not bearing sulfonate-

tagged ligands is soluble in both phases arising from the mixture

[BMIM]OTf/toluene⁴⁰and thus shows strong leaching while

complex 16 having a sulfonated DAD^Sligand is completely

retained in the polar, IL-rich phase. No visible leaching of 16 into

the toluene layer was observed even in contact to concentrated IL

solutions. As this intensely coloured complex is clearly visible at

concentrations of about 0.1 mmol L^-1and the saturation limit in

pure [BMIM]OTf exceeds 100 mmol L^-1, the distribution ratio of

the DAD^Scomplex 16 can be estimated to be at least 1000 : 1 in

favour of the IL phase.

Fig. 5 Molecular structure of 12d. Displacement ellipsoids are shown

for 50% probability, carbon-bound hydrogen atoms are omitted for

clarity. Selected bond lengths (pm) and angles (^◦): Pd1–N101 202.2(4),

Pd1–N102 201.2(4), Pd1–Cl1 231.8(2), Pd1–Cl2 228.2(2), C101–N101

128.6(6), C111–N102 129.5(6), C101–C111 148.4(8), N101–C103 140.8(7),

N102–C113 143.4(7); N101–Pd1–N102 79.5(2), N101–Pd1–Cl1 95.4(2),

N102–Pd1–Cl2 94.3(2), Cl1–Pd1–Cl2 91.1(1), C101–N101–Pd1 113.8(4),

C111–N102–Pd1 116.0(4), C103–N101–Pd1 125.5(3), C113–N102–Pd1

124.0(3), C101–N101–C103 120.6(4), C111–N102–C113 119.9(4);

N101–C101–C111–N102 3.0(6), C101–N101–C103–C104 83.6(6), C101–

N101–C103–C108 98.0(5), C111–N102–C113–C114 90.4(6), C111–N102–

C113–C118 92.5(6).

angle of 79.5^◦. Due to the chelating metal coordination, cis

conformation is found for the diimine moiety. The aromatic

substituents feature torsion angles towards the diimine fragment

that are similar to the free ligands (84 and 91^◦, respectively). All

main geometric characteristics are thus comparable to palladium

dichloro complexes of non-sulfonated DAD ligands such as

[PdCl₂(2,6-iPr₂-Me-DAD)]³⁸and [PdCl₂(2,6-iPr₂-H-DAD)].³⁹

As expected for acidic ammonium salts, 4a and 12d clearly

show N–H ◊ ◊ ◊ O hydrogen bonding (N ◊ ◊ ◊ O = 299–334 pm). For

all imidazolium-based salts, a relatively short contact between the

N-methyl group and the sulfonate groups is found (C ◊ ◊ ◊ O = 310–

318 pm). In the case of 6, additional short contacts exist between

all three imidazolium carbon atoms and the sulfonate groups (319–

322 pm), indicating C–H ◊ ◊ ◊ O hydrogen bonding.

Both 8b and 8c show short contacts between the sulfonate

moieties and C201 (C ◊ ◊ ◊ O = 295 and 304 pm) as well as C202

(C ◊ ◊ ◊ O = 319 and 309 pm). Interestingly, no such interaction is

found for C203 and C208, although the latter position is selectively

deprotonated with strong bases, yielding the corresponding N,N-

ketenediacetals (cf . Scheme 2).

The crystal packings of 4a, 8b, 8c and 12d form layered

structures with alternating polar (anionic and cationic head

groups) and unpolar layers (aromatics, diimine motif and N-butyl

groups) as shown for 8c in Fig. 6.

Fig. 7 Different distribution behaviour of molybdenum carbonyl com-

plexes in [BMIM]OTf/toluene for a “classical”, non-sulfonated DAD

ligand (left, 15) and a sulfonated DAD^Sligand (right, 16).

Table 4 Solubility of molybdenum carbonyl complexes in [BMIM]OTf

15

16

DAD ligand

_max/nm

e/M^-1cm^-1

(2,6-Me₂-Me-DAD) [BMMIM]₂[2,6-Me₂-Me-DAD^S]

l

525

6290

525

5340

104

80

Solubility^a/g L^-13.3

w

_max/mg g^-1

c_max^a/mmol L^-1

2.6

6.8

108

Fig. 6 Crystal packing of 8c, view along the b axis. Sulfonate and

imidazolium groups are shown in grey, diimines, aromatics and butyl

groups in white. Hydrogens are omitted.

^aDensity (solution) = density (pure IL) is assumed.

12732 | Dalton Trans., 2011, 40, 12727–12741

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Conclusions

Sulfonate-tagged diazadiene (DAD^S) ligands have been shown

to be easily accessible, versatile building blocks for transition-

metal catalysts in multiphasic IL systems. Prominent basic cation

precursors also used in the high-purity synthesis of ILs provide a

reliable route towards completely halide-free and metal-free DAD^S

ligands with onium cations. These well IL-soluble ligands show

similar behaviour in complexation reactions as the corresponding

neutral parent compounds and can thus be used to generate

prominent catalyst precursor analogues with optimised solubility

and retention in ILs. Additional studies will be undertaken in the

future regarding further catalytically attractive metal complexes

and their evaluation in biphasic homogeneous catalysis based on

ILs. Preliminary results suggest that zwitterionic DAD^Scomplexes

of Pd(II) and Pt(II) bearing neutral coligands are potentially

valuable catalyst precursors. The pronounced solvatochromic

behaviour of DAD and DAD^Smolybdenum carbonyl complexes

offers another interesting subject for further studies on the polarity

of ILs as compared to conventional solvents.

Scheme 8 Numbering of cations and anions.

0.95 to 0.98 for all four elements. These differences are most likely

attributed to the poor combustion of the ionic compounds.

UV-Vis spectra were taken on a Novaspec II spectrophotometer

at room temperature. Absorption at l_max(525 nm) was measured

for six calibration standards in the concentration range of 0.1

to 1 mg mL^-1for both complexes. Saturated solutions of the

complexes were obtained by stirring an excess of the solute with

1 mL of the IL for three days at room temperature, followed by

ﬁltration via 0.45 mm syringe ﬁlters. Weighted samples of these

stock solutions were diluted using [BMIM]OTf to give absorptions

similar to the calibration standards and measured. Concentrations

were determined according to Lambert–Beer’s law.

Experimental

General remarks

Manipulation of air- and moisture-sensitive substances was

carried out using standard Schlenk- and glovebox-techniques.

Solvents were dried using standard procedures⁴¹and stored over

˚

Al₂O₃/molecular sieve 3 A/R3-11G catalyst (BASF).

Sulfanilic acids,¹⁴imidazoline-2-ylidenes,¹⁵2-methylidene-

imidazolines,¹⁶methylidenephosphoranes¹⁷and guanidinium

methylcarbonates¹⁸were prepared according to the literature.

[BMIM]OTf (99%, MERCK) was degassed and stored in a glovebox.

Other starting materials were obtained from commercial sources

(SIGMA-ALDRICH, MERCK, IOLITEC) and used as received.

Synthesis of compounds

Triethylammonium dialkylsulfanilates

General procedure for the preparation of triethylammonium di-

alkylsulfanilates (3a–c). The appropriate sulfanilic acid 2 (1.0 eq)

was suspended in a sufﬁcient amount of methanol to allow

for magnetic stirring. Triethylamine (1.1–1.3 eq) was added and

the mixture was stirred for 15 min at room temperature. Any

insoluble matter was removed by ﬁltration; the resulting solution

was concentrated and dried in vacuo. The obtained crude product

was extracted with ether and dried in vacuo.

NMR spectra were recorded at 300 K on a BRUKER AC 300,

DRX 400 or DRX 500 using CD₃CN or DMSO-d₆as solvent.

Chemical shifts are given with respect to tetramethylsilane (¹H,

¹³C), phosphoric acid (³¹P) and Na₂[PtCl₆] (¹⁹⁵Pt), respectively.

1

Calibration of H and ¹³C NMR spectra was accomplished with

the solvent signals, ³¹P and ¹⁹⁵Pt NMR spectra were calibrated

externally.

For facile differentiation of anion and cation signals the former

are denoted with the subscript “_A” while the latter are identiﬁed

using the subscript “_C”. The applied numbering schemes are shown

in Scheme 8. Only half a molecule is shown for the DAD^Sligand

anions because of the magnetic equivalence of both moieties that

was observed for all ligands and complexes.

ESI mass spectra were recorded on a THERMO FISHER SCIENTIFIC

LTQ FT Ultra using acetonitrile as solvent. m/z values are given

together with their relative intensities. Isotopic patterns were in all

cases consistent with natural abundances.

IR spectra were recorded on a BRUKER Alpha FT-IR spectrome-

ter using neat samples with an ATR measurement setup (diamond

cell) at room temperature.

Elemental analysis was done on a CHN/S vario MICROcube

(ELEMENTAR). Values are given in weight percent. Satisfactory

analyses could not be obtained for all new compounds. In most

aberrant cases, the measured values were too low by a factor of

Triethylammonium 2,6-dimethylaniline-4-sulfonate (3a). Pre-

pared from 2,6-dimethylaniline-4-sulfonic acid (2a) (12.00 g,

59.6 mmol, 1.00 eq) and triethylamine (7.24 g, 71.6 mmol, 1.20 eq):

17.21 g (95%) light brown powder. Anal. calc. for C₁₄H₂₆N₂O₃S

(302.43 g mol^-1) C 55.60, H 8.67, N 9.26, S 10.60%; found C

1

55.08, H 8.83, N 8.84, S 9.74%. H NMR (300 MHz, D₂O) d =

1.15 (t, 9H, ³J_HH= 7.3 Hz, C2_C-H), 2.10 (s, 6H, C5_A-H), 3.02 (q,

3

6H, J_HH= 7.3 Hz, C1_C-H), 7.32 (s, 2H, C3_A-H) ppm; ¹³C NMR

(75 MHz, D₂O) d = 8.4 (C2_C), 17.1 (C5_A), 46.9 (C1_C), 123.2 (C2_A),

125.5 (C3_A), 132.4 (C4_A), 145.8 (C1_A) ppm. MS (ESI+) m/z (%) =

102.1252 (100, C₆H₁₆N requires 102.1277, [cation]⁺); MS (ESI-)

m/z (%) = 200.0375 (100, C₈H₁₀NO₃S requires 200.0387, [anion]^-).

IR (neat) n = 3459 (w), 3366 (w), 2982 (w), 2695 (br w), 1632

(w), 1481 (m), 1458 (w), 1443 (w), 1389 (w), 1294 (w), 1210 (s),

1180 (m), 1151 (s), 1115 (s), 1029 (vs), 1011 (m), 886 (w), 840 (w),

748 (w), 634 (vs), 612 (m) cm^-1.

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Triethylammonium 2,4,6-trimethylaniline-3-sulfonate (3b).

Prepared from 2,4,6-trimethylaniline-3-sulfonic acid (2b) (20.00 g,

92.9 mmol, 1.00 eq) and triethylamine (10.12 g, 100 mmol,

1.08 eq): 28.61 g (97%) light brown powder. ¹H NMR (300 MHz,

C1_C-H), 7.34 (s, 4H, C5_A-H), 8.97 (br s, 2H, NH⁺) ppm; ¹³C

NMR (75 MHz, DMSO-d₆) d = 8.5 (C2_C), 15.6 (C2_A), 17.3 (C7_A),

45.7 (C1_C), 123.3 (C4_A), 125.3 (C5_A), 142.8 (C6_A), 148.2 (C3_A),

167.7 (C1_A) ppm. MS (ESI+) m/z (%) = 102.1276 (100, C₆H₁₆N

requires 102.1277, [cation]⁺); MS (ESI-) m/z (%) = 225.0455 (100,

C₂₀H₂₂N₂O₆S₂requires 225.0465, [anion]^2-), 451 (23, [anion +

H]^-). IR (neat) n = 2983 (w), 2691 (br w), 1641 (m), 1473 (m),

1453 (w), 1393 (w), 1362 (w), 1224 (s), 1157 (s), 1123 (m), 1107

(s), 1032 (vs), 886 (m), 839 (w), 786 (w), 647 (vs), 628 (vs), 589

(m), 554 (m), 523 (m), 497 (m), 444 (w) cm^-1.

3

DMSO-d₆) d = 1.16 (t, 9H, J_HH= 7.3 Hz, C2_C-H), 2.04, 2.38,

2.40 (3 ¥ s, 3 ¥ 3H, C7-9_A-H), 3.04 (q, 6H, ³J_HH= 7.3 Hz, C1_C-H),

4.29 (s, 2H, NH₂), 6.60 (s, 1H, C5_A-H), 9.46 (br s, 1H, NH⁺) ppm;

¹³C NMR (75 MHz, DMSO-d₆) d = 8.5 (C2_C), 15.4, 17.7, 22.7

(C7-9_A), 45.7 (C1_C), 120.0, 121.1, 122.9 (C2_A, C4_Aand C6_A),

130.4 (C5_A), 142.4 (C3_A), 143.2 (C1_A) ppm. MS (ESI+) m/z

(%) = 102.1278 (100, C₆H₁₆N requires 102.1277, [cation]⁺), 418

(24, [2 ¥ cation + anion]⁺); MS (ESI-) m/z (%) = 214.0540 (100,

C₉H₁₂NO₃S requires 214.0543, [anion]^-). IR (neat) n = 3381 (w),

3016 (br w), 2980 (w), 2702 (br w), 1623 (w), 1476 (w), 1459 (m),

1387 (w), 1303 (w), 1221 (m), 1201 (m), 1178 (m), 1151 (m), 1051

(s), 1010 (m), 986 (m), 897 (w), 841 (w), 812 (w), 669 (vs), 599 (m),

577 (m), 546 (s), 519 (m), 470 (m) cm^-1.

Bis(triethylammonium) N,N¢-bis(2,4,6-trimethyl-3-sulfonato-

phenyl)butane-2,3-diimine (4b) [HNEt₃]₂[2,4,6-Me₃-Me-DAD^S].

Prepared from triethylammonium 2,4,6-trimethylaniline-3-

sulfonate (3b) (1.00 g, 3.16 mmol, 2.00 eq) and butane-2,3-dione

(0.14 mL, 1.59 mmol, 1.02 eq): 0.44 g (41%) yellow powder. Anal.

calc. for C₃₄H₅₈N₄O₆S₂(682.98 g mol^-1) C 59.79, H 8.56, N 8.20,

S 9.39%; found C 59.44, H 8.39, N 8.06, S 9.03%. ¹H NMR

Triethylammonium 2,6-diisopropylaniline-4-sulfonate (3c). Pre-

pared from 2,6-diisopropylaniline-4-sulfonic acid monohydrate

(2c) (12.17 g, 44.2 mmol, 1.00 eq) and triethylamine (5.31 g,

53.0 mmol, 1.20 eq): 15.50 g (98%) light brown powder. Anal.

calc. for C₁₈H₃₄N₂O₃S (358.54 g mol^-1) C 60.30, H 9.56, N 7.81,

S 8.94%; found C 60.02, H 9.45, N 7.71, S 8.45%. ¹H NMR

3

(300 MHz, DMSO-d₆) d = 1.17 (t, 18H, J_HH= 7.3 Hz, C2_C-H),

1.88, 1.89 (2 ¥ s, 6H, C11_A-H, conformers), 1.91 (s, 6H, C2_A-H),

2.22, 2.24 (2 ¥ s, 6H, C9_A-H, conformers), 2.51 (s, 6H, C10_A-H),

3.08 (q, 12H, ³J_HH= 7.3 Hz, C1_C-H), 6.85 (s, 2H, C7_A-H), 9.08 (br

s, 2H, NH⁺) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 8.6 (C2_C),

15.57, 15.59 (C2_A, conformers), 15.8, 15.9 (C9_A, conformers),

17.2, 17.3 (C11_A, conformers), 22.7 (C10_A), 45.8 (C1_C), 123.2,

123.29, 123.32, 123.4, 130.2 (C4_A, C6_Aand C6_A, conformers),

130.6 (C7_A), 143.9 (C5_A), 146.6 (C3_A), 167.8 (C1_A) ppm. MS

(ESI+) m/z (%) = 102.1277 (100, C₆H₁₆N requires 102.1277,

[cation]⁺); MS (ESI-) m/z (%) = 239.0619 (100, C₂₂H₂₆N₂O₆S₂

requires 239.0622, [anion]^2-), 479 (28, [anion + H]^-). IR (neat) n =

2982 (w), 2926 (w), 2698 (br w), 1649 (m), 1451 (m), 1401 (w),

1360 (w), 1223 (s), 1166 (vs), 1125 (m), 1049 (s), 1014 (m), 991 (s),

869 (w), 803 (w), 751 (w), 695 (m), 658 (vs), 628 (s), 595 (w), 578

(m), 559 (m), 543 (s), 523 (m), 467 (w) cm^-1.

3

(300 MHz, D₂O) d = 1.17 (d, 12H, J_HH= 6.7 Hz, C6_A-H), 1.18

3

(t, 9H, J_HH= 7.3 Hz, C2_C-H), 2.94 (sept, 2H, J_HH= 6.8 Hz,

3

C5_A-H), 3.07 (q, 6H, J_HH= 7.3 Hz, C1_C-H), 7.45 (s, 2H, C3_A-

H) ppm; ¹³C NMR (75 MHz, D₂O) d = 8.3 (C2_C), 21.8 (C6_A),

27.3 (C5_A), 46.7 (C1_C), 120.4 (C3_A), 132.9 (C4_A), 133.9 (C2_A),

143.0 (C1_A) ppm. MS (ESI+) m/z (%) = 102.1276 (100, C₆H₁₆N

requires 102.1277, [cation]⁺); MS (ESI-) m/z (%) = 256.1009 (100,

C₁₂H₁₈NO₃S requires 256.1002, [anion]^-). IR (neat) n = 3440 (w),

3362 (w), 3266 (w), 2964 (m), 2637 (br w), 2495 (w), 1641 (m), 1461

(m), 1437 (m), 1384 (w), 1357 (w), 1285 (w), 1202 (s), 1150 (s),

1119 (m), 1072 (s), 1026 (vs), 885 (w), 838 (w), 759 (w), 636 (vs),

616 (s), 535 (m) cm^-1.

Triethylammonium DAD^S

Bis(triethylammonium) N,N¢-bis(2,6-diisopropyl-4-sulfonato-

phenyl)butane-2,3-diimine (4c) [HNEt₃]₂[2,6-iPr₂-Me-DAD^S].

Prepared from triethylammonium 2,6-diisopropylaniline-4-

sulfonate (3c) (3.02 g, 8.40 mmol, 2.00 eq) and butane-2,3-dione

(0.6 mL, 6.46 mmol, 1.54 eq): 0.58 g (18%) yellow powder.

Anal. calc. for C₄₀H₇₀N₄O₆S₂(767.14 g mol^-1) C 62.63, H 9.20,

General procedure for the preparation of triethylammonium

salts of DAD^Sligands (4a–c). A solution of the appropriate

triethylammonium sulfanilate 3 (2.0 eq), butane-2,3-dione (1.0–

1.5 eq) and formic acid (0.05 eq) in methanol (100 mL) was

heated to 40 ^◦C for 24 h. The resulting brown solution was

evaporated to dryness. The crude product was suspended in ether

and sonicated until a powdery solid had formed. After drying, this

solid was recrystallized from acetonitrile or acetonitrile/ether. In

most cases, two or three additional crops of product were obtained

from the mother liquor upon cooling and further addition of

ether.

1

N 7.30, S 8.36%; found C 62.21, H 9.06, N 7.23, S 7.99%. H

3

NMR (300 MHz, DMSO-d₆) d = 1.10 (d, 12H, J_HH= 6.9 Hz,

3

C8a_A-H), 1.16 (d, 12H, J_HH= 6.9 Hz, C8b_A-H), 1.17 (t, 18H,

³J_HH= 7.2 Hz, C2_C-H), 2.00 (s, 6H, C2_A-H), 2.68 (sept, 4H, ³J_HH

=

3

6.8 Hz, C7_A-H), 3.09 (dq, 12H, J_HH= 4.7, 7.3 Hz, C1_C-H), 7.44

(s, 4H, C5_A-H), 8.98 (br s, 2H, NH⁺) ppm; ¹³C NMR (75 MHz,

DMSO-d₆) d = 8.6 (C2_C), 16.3 (C2_A), 22.2 (C8a_A), 22.7 (C8b_A),

28.0 (C7_A), 45.8 (C1_C), 120.4 (C5_A), 133.7 (C4_A), 143.6 (C6_A),

145.9 (C3_A), 168.0 (C1_A) ppm. MS (ESI+) m/z (%) = 102.1278

(100, C₆H₁₆N requires 102.1277, [cation]⁺); MS (ESI-) m/z (%) =

281.1084 (100, C₂₈H₃₈N₂O₆S₂requires 281.1091, [anion]^2-), 563

(4, [anion + H]^-). IR (neat) n = 2967 (w), 2705 (br w), 1655 (w),

1465 (w), 1430 (w), 1361 (w), 1224 (m), 1166 (s), 1151 (s), 1118

(m), 1070 (m), 1029 (vs), 888 (w), 847 (w), 801 (w), 650 (m), 639

(s), 618 (s), 607 (m), 556 (w), 538 (w), 520 (w), 497 (w), 467 (w),

445 (w) cm^-1.

Bis(triethylammonium) N,N¢-bis(2,6-dimethyl-4-sulfonatoph-

enyl)butane-2,3-diimine

Prepared from triethylammonium 2,6-dimethylaniline-4-sulfonate

(3a) (10.61 g, 35.1 mmol, 2.00 eq) and butane-2,3-dione (2.4 mL,

26.9 mmol, 1.53 eq): 5.11 g (44%) yellow powder. Anal. calc. for

C₃₂H₅₄N₄O₆S₂(654.92 g mol^-1) C 58.68, H 8.31, N 8.55, S 9.79%;

(4a)

[HNEt₃]₂[2,6-Me₂-Me-DAD^S].

1

found C 58.36, H 8.46, N 8.46, S 9.47%. H NMR (300 MHz,

3

DMSO-d₆) d = 1.17 (t, 18H, J_HH= 7.3 Hz, C2_C-H), 1.96 (s, 6H,

C2_A-H), 1.97 (s, 12H, C7_A-H), 3.09 (dq, 12H, ³J_HH= 4.9, 7.3 Hz,

12734 | Dalton Trans., 2011, 40, 12727–12741

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Imidazolium DAD^Sand related

(C6_C), 122.2 (C5_C), 123.2 (C4_A), 123.6 (C4_C), 125.2 (C5_A), 136.5

(C2_C), 143.3 (C6_A), 148.0 (C3_A), 167.7 (C1_A) ppm. MS (ESI+) m/z

(%) = 139.1229 (100, C₈H₁₅N₂requires 139.1230, [cation]⁺); MS

(ESI-) m/z (%) = 225 (100, [anion]^2-), 451.0982 (17, C₂₀H₂₃N₂O₆S₂

requires 451.0992, [anion + H]^-), 589 (7, [anion + cation]^-). IR

(neat) n = 3094 (w), 2959 (w), 2872 (w), 1631 (w), 1569 (w), 1456

(w), 1359 (w), 1233 (w), 1209 (m), 1173 (s), 1124 (m), 1103 (m),

1035 (s), 886 (w), 877 (w), 853 (w), 783 (w), 641 (s), 629 (m), 619

(s), 586 (m), 556 (m), 522 (m), 497 (m) cm^-1.

General procedure for the preparation of onium-salts of

DAD^Sligands (5–8, 10) from imidazoline-2-ylidenes, 2-

methylideneimidazolines or methylidenephosphoranes. A solution

or suspension of the appropriate triethylammonium DAD^S4 (0.2–

5 g, 1.0 eq) in acetonitrile (10–40 mL) was cooled to -40 ^◦C.

The appropriate cation precursor (2.2 eq) was slowly added via

syringe. The mixture was allowed to warm to room temperature

overnight. After removal of all volatiles in vacuo the crude product

was washed with ether and dried at 10^-2mbar.

The same product was obtained from 4a (1.96 g, 3.00 mmol,

1.00 eq) and 1-n-butyl-3-methylimidazoline-2-ylidene (0.87 g,

6.30 mmol, 2.10 eq): 1.30 g (59%) yellow powder.

The obtained ligand salts can be further puriﬁed by recrys-

tallization from acetonitrile/ether or dichloromethane/ether, if

necessary.

Bis(1,3-diisopropylimidazolium)

N,N¢-bis(2,6-dimethyl-4-

sulfonatophenyl)butane-2,3-diimine (7) [DIIM]₂[2,6-Me₂-Me-

DAD^S]. Prepared from 4a (1.00 g, 1.53 mmol, 1.00 eq) and

1,3-diisopropylimidazoline-2-ylidene (0.50 g, 3.28 mmol, 2.14 eq):

1.13 g (98%) light yellow powder. Anal. calc. for C₃₈H₅₆N₆O₆S₂

(757.02 g mol^-1) C 60.29, H 7.46, N 11.10, S 8.47%; found C

59.93, H 7.40, N 11.18, S 7.88%. ¹H NMR (300 MHz, DMSO-d₆)

d = 1.47 (d, 24H, ³J_HH= 6.6 Hz, C7_C-H), 1.96 (s, 6H, C2_A-H), 1.97

General procedure for the preparation of onium-salts of DAD^S

ligands (6, 9, 11) from ammonium hydroxides, imidazolium

methylcarbonates or guanidinium methylcarbonates

The same procedure as above was applied, except that no cooling

of the reaction mixture was needed with these less sensitive

cation precursors. Thus, the reaction was carried out at room

temperature.

3

(s, 12H, C7_A-H), 4.62 (sept, 4H, J_HH= 6.7 Hz, C6_C-H), 7.34 (s,

4H, C5_A-H), 7.93 (d, 4H, ⁴J_HH= 1.2 Hz, C4_C-H and C5_C-H), 9.32

(s, 2H, C2_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 15.6

(C2_A), 17.3 (C7_A), 22.3 (C7_C), 52.2 (C6_C), 120.6 (C4_Cand C5_C),

123.2 (C4_A), 125.2 (C5_A), 133.6 (C2_C), 143.3 (C6_A), 148.0 (C3_A),

167.7 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1387 (100, C₉H₁₇N₂

requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) = 225.0455

(100, C₂₀H₂₂N₂O₆S₂requires 225.0465, [anion]^2-), 603 (5, [anion +

cation]^-). IR (neat) n = 3087 (w), 3039 (w), 2977 (w), 1639 (m),

1556 (w), 1464 (w), 1435 (w), 1377 (w), 1357 (w), 1271 (w), 1236

(m), 1210 (s), 1185 (s), 1152 (m), 1107 (m), 1038 (s), 883 (m), 784

(w), 662 (w), 641 (s), 628 (s), 608 (w), 587 (w), 555 (w), 522 (w),

497 (w) cm^-1.

Bis(1-ethyl-3-methylimidazolium)

N,N¢-bis(2,6-dimethyl-4-

sulfonatophenyl)butane-2,3-diimine (5) [EMIM]₂[2,6-Me₂-Me-

DAD^S]. Prepared from 4a (2.09 g, 3.18 mmol, 1.00 eq) and

1-ethyl-3-methylimidazoline-2-ylidene (0.77 g, 6.99 mmol,

2.20 eq): 1.91 g (89%) light yellow powder. Anal. calc. for

C₃₂H₄₄N₆O₆S₂(672.86 g mol^-1) C 57.12, H 6.59, N 12.49, S 9.53%;

1

found C 56.92, H 6.64, N 12.44, S 9.18%. H NMR (300 MHz,

3

CD₃CN) d = 1.44 (t, 6H, J_HH= 7.3 Hz, C7_C-H), 1.99 (s, 6H,

C2_A-H), 2.01 (s, 12H, C7_A-H), 3.83 (s, 6H, C8_C-H), 4.17 (q, 4H,

³J_HH= 7.3 Hz, C6_C-H), 7.34, 7.39 (2 ¥ s, 2 ¥ 2H, C4_C-H and

C5_C-H), 7.45 (s, 4H, C5_A-H), 8.80 (s, 2H, C2_C-H) ppm; ¹³C NMR

(75 MHz, CD₃CN) d = 15.6 (C2_A), 16.2 (C7_C), 18.0 (C7_A), 36.7

(C8_C), 45.7 (C6_C), 125.1 (C4_A), 126.4 (C5_A), 144.6 (C6_A), 149.7

(C3_A), 169.2 (C1_A) ppm. MS (ESI+) m/z (%) = 111.0916 (100,

C₆H₁₁N₂requires 111.0917, [cation]⁺); MS (ESI-) m/z (%) = 225

(6, [anion]^2-), 451.1011 (100, C₂₀H₂₃N₂O₆S₂requires 451.1003,

[anion + H]^-). IR (neat) n = 3096 (w), 1646 (w), 1574 (w), 1457

(br w), 1363 (w), 1209 (m), 1180 (s), 1127 (m), 1105 (m), 1035 (s),

888 (w), 872 (w), 835 (w), 784 (w), 645 (s), 621 (s), 587 (m), 554

(w), 522 (w), 498 (w) cm^-1.

Bis(1-n-butyl-2,3-dimethylimidazolium) N,N¢-bis(2,6-dimethyl-

4-sulfonatophenyl)butane-2,3-diimine (8a) [BMMIM]₂[2,6-Me₂-

Me-DAD^S]. Prepared from 4a (2.02 g, 3.08 mmol, 1.00 eq) and

1-n-butyl-2-methylidene-3-methylimidazoline (1.13 g, 7.40 mmol,

2.40 eq): 2.28 g (98%) yellow powder. Anal. calc. for C₃₈H₅₆N₆O₆S₂

(757.02 g mol^-1) C 60.29, H 7.46, N 11.10, S 8.47%; found C 59.80,

1

H 7.35, N 11.01, S 8.20%. H NMR (300 MHz, DMSO-d₆) d =

0.90 (t, 6H, ³J_HH= 7.3 Hz, C9_C-H), 1.27 (psext, 4H, ³J_HH= 7.6 Hz,

3

Bis(1-n-butyl-3-methylimidazolium) N,N¢-bis(2,6-dimethyl-4-

sulfonatophenyl)butane-2,3-diimine (6) [BMIM]₂[2,6-Me₂-Me-

DAD^S]. Prepared from 4a (215 mg, 0.33 mmol, 1.00 eq) and

a methanolic solution (50%) of 1-n-butyl-3-methylimidazolium

methylcarbonate (0.3 mL, corresponds to 0.68 mmol, 2.05 eq):

238 mg (99%) light yellow powder. Anal. calc. for C₃₆H₅₂N₆O₆S₂

(728.97 g mol^-1) C 59.31, H 7.19, N 11.53, S 8.80%; found C

58.64, H 7.34, N 11.56, S 7.88%. ¹H NMR (300 MHz, DMSO-d₆)

C8_C-H), 1.68 (pquint, 4H, J_HH= 7.5 Hz, C7_C-H), 1.96 (s, 6H,

C2_A-H), 1.97 (s, 12H, C7_A-H), 2.57 (s, 6H, C10_C-H), 3.74 (s, 6H,

C11_C-H), 4.10 (t, 4H, ³J_HH= 7.3 Hz, C6_C-H), 7.31 (s, 4H, C5_A-H),

3

7.62 (d, 2H, J_HH= 2.1 Hz, C4_C-H), 7.65 (d, 2H, J_HH= 2.1 Hz,

C5_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 9.1 (C10_C),

13.3 (C9_C), 15.6 (C2_A), 17.3 (C7_A), 18.8 (C8_C), 31.1 (C7_C), 34.6

(C11_C), 47.2 (C6_C), 120.8 (C5_C), 122.3 (C4_C), 123.1 (C4_A), 125.2

(C5_A), 143.4 (C6_A), 144.2 (C2_C), 147.9 (C3_A), 167.6 (C1_A) ppm.

MS (ESI+) m/z (%) = 153.1386 (100, C₉H₁₇N₂requires 153.1386,

[cation]⁺); MS (ESI-) m/z (%) = 225.0460 (100, C₂₀H₂₂N₂O₆S₂

requires 225.0465, [anion]^2-), 603 (13, [anion + cation]^-). IR (neat)

n = 3097 (w), 2960 (w), 1652 (w), 1589 (w), 1542 (w), 1462 (w),

1436 (w), 1361 (w), 1193 (vs), 1108 (m), 1039 (s), 889 (w), 875 (w),

794 (m), 670 (w), 646 (s), 627 (m), 609 (w), 587 (w), 554 (w), 519

(w), 498 (w), 441 (w) cm^-1.

3

d = 0.89 (t, 6H, J_HH= 7.3 Hz, C9_C-H), 1.24 (psext, 4H, J_HH

=

3

7.5 Hz, C8_C-H), 1.75 (pquint, 4H, J_HH= 7.4 Hz, C7_C-H), 1.95

(s, 6H, C2_A-H), 1.96 (s, 12H, C7_A-H), 3.84 (s, 6H, C10_C-H), 4.15

3

(t, 4H, J_HH= 7.2 Hz, C6_C-H), 7.33 (s, 4H, C5_A-H), 7.71 (t, 2H,

³J_HH= 1.7 Hz, C4_C-H), 7.78 (t, 2H, ³J_HH= 1.7 Hz, C5_C-H), 9.15 (s,

2H, C2_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 13.2 (C9_C),

15.6 (C2_A), 17.3 (C7_A), 18.7 (C8_C), 31.3 (C7_C), 35.7 (C10_C), 48.4

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Bis(tri-n-butylmethylphosphonium)

N,N¢-bis(2,6-dimethyl-4-

167.7 (C1_A) ppm. MS (ESI+) m/z (%) = 354.3842 (100, C₂₂H₄₈N₃

requires 354.3843, [cation]⁺); MS (ESI-) m/z (%) = 451.1015 (100,

C₂₀H₂₃N₂O₆S₂requires 451.1003, [anion + H]^-), 804 (20, [anion +

cation]^-). IR (neat) n = 2956 (m), 2930 (m), 2871 (w), 1644 (w),

1537 (m), 1457 (m), 1376 (w), 1360 (w), 1313 (w), 1270 (w), 1235

(w), 1196 (vs), 1106 (m), 1035 (vs), 886 (m), 738 (w), 645 (s), 627

(s), 605 (w), 587 (w), 553 (w), 520 (w), 497 (w) cm^-1.

sulfonatophenyl)butane-2,3-diimine (9) [Bu₃PMe]₂[2,6-Me₂-Me-

DAD^S]. Prepared from 4a (301 mg, 0.46 mmol, 1.00 eq) and

tri-n-butylmethylidenephosphorane (200 mg, 0.92 mmol, 2.02 eq):

370 mg (91%) light yellow powder. Anal. calc. for C₄₆H₈₂N₂O₆P₂S₂

(885.23 g mol^-1) C 62.41, H 9.34, N 3.16, S 7.24%; found C 61.90,

1

H 9.18, N 3.49, S 6.87%. H NMR (300 MHz, DMSO-d₆) d =

3

0.91 (t, 18H, J_HH= 6.9 Hz, C4_C-H), 1.33–1.52 (m, 24H, C3_C-H

and C2_C-H), 1.79 (d, 6H, ²J_PH= 14 Hz, C5_C), 1.96 (s, 6H, C2_A-H),

Bis(1-n-butyl-2,3-dimethylimidazolium) N,N¢-bis(2,4,6-trime-

thyl-3-sulfonatophenyl)butane-2,3-diimine (8b) [BMMIM]₂[2,4,6-

Me₃-Me-DAD^S]. Prepared from 4b (1.00 g, 1.47 mmol, 1.00 eq)

and 1-n-butyl-2-methylidene-3-methylimidazoline (0.54 g,

3.53 mmol, 2.40 eq): 1.04 g (91%) yellow powder. ¹H NMR

1.97 (s, 12H, C7_A-H), 2.08–2.21 (m, 12H, C1_C-H), 7.33 (s, 4H,

C5_A-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 3.1 (d, J_PC

1

=

1

51 Hz, C5_C), 13.2 (C4_C), 15.6 (C2_A), 17.3 (C7_A), 18.9 (d, J_PC

2

3

49 Hz, C1_C), 22.6 (d, J_PC= 4.4 Hz, C2_C), 23.3 (d, J_PC= 16 Hz,

C3_C), 123.2 (C4_A), 125.2 (C5_A), 143.4 (C6_A), 148.0 (C3_A), 167.7

(C1_A) ppm; ³¹P NMR (121 MHz, DMSO-d₆) d = 32.2 ppm. MS

(ESI+) m/z (%) = 217.2079 (100, C₁₃H₃₀P requires 217.2080,

[cation]⁺); MS (ESI-) m/z (%) = 225.0455 (100, C₂₀H₂₂N₂O₆S₂

requires 225.0465, [anion]^2-), 668 (5, [anion + cation]^-). IR (neat)

n = 2959 (w), 2931 (w), 2906 (w), 2869 (w), 1651 (w), 1464 (w),

1209 (m), 1188 (s), 1123 (w), 1105 (m), 1035 (s), 1003 (w), 941

(m), 931 (m), 909 (w), 898 (w), 879 (w), 783 (w), 645 (s), 626 (s),

588 (m), 553 (w), 520 (w), 498 (w) cm^-1.

3

(300 MHz, DMSO-d₆) d = 0.88 (t, 6H, J_HH= 7.3 Hz, C9_C-H),

1.26 (psext, 4H, ³J_HH= 7.5 Hz, C8_C-H), 1.66 (pquint, 4H, ³J_HH

=

7.4 Hz, C7_C-H), 1.87, 1.89 (2 ¥ s, 6H, C11_A-H, conformers), 1.90

(s, 6H, C2_A-H), 2.22, 2.23 (2 ¥ s, 6H, C9_A-H, conformers), 2.50

(s, 6H, C10_A-H), 2.56 (s, 6H, C10_C-H), 3.74 (s, 6H, C11_C-H),

3

4.09 (t, 4H, J_HH= 7.3 Hz, C6_C-H), 6.84 (s, 2H, C7_A-H), 7.63

3

(d, 2H, J_HH= 1.8 Hz, C4_C-H), 7.66 (d, 2H, J_HH= 1.8 Hz,

C5_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 9.1 (C10_C),

13.3 (C9_C), 15.5 (C2_A), 15.8, 15.9 (C9_A, conformers), 17.2, 17.3

(C11_A, conformers), 18.8 (C8_C), 22.7 (C10_A), 31.1 (C7_C), 34.6

(C11_C), 47.2 (C6_C), 120.8 (C5_C), 122.3 (C4_C), 123.1, 123.2, 130.1

(C4_A, C6_Aand C8_A), 130.6 (C7_A), 144.12 (C5_A), 144.14 (C2_C),

146.6 (C3_A), 167.7 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1385

(100, C₉H₁₇N₂requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) =

479.1329 (100, C₂₂H₂₇N₂O₆S₂requires 479.1316, [anion + H]^-).

IR (neat) n = 3097 (w), 2954 (w), 1646 (w), 1588 (w), 1540 (w),

1457 (w), 1434 (w), 1374 (w), 1360 (w), 1239 (m) 1220 (s), 1181

(vs), 1122 (m), 1049 (s), 1016 (w), 992 (m), 864 (w), 790 (m), 763

(w), 695 (m), 669 (m), 659 (s), 631 (s), 579 (w), 560 (m), 538 (m),

527 (m) cm^-1.

Bis(tetra-n-butylammonium) N,N¢-bis(2,6-dimethyl-4-sulfona-

tophenyl)butane-2,3-diimine (10) [Bu₄N]₂[2,6-Me₂-Me-DAD^S].

Prepared from 4a (510 mg, 0.78 mmol, 1.00 eq) and tetra-n-

butylammonium hydroxide (3.6 mL of a 12.5 wt% solution in

methanol, 1.39 mmol, 1.78 eq): 640 mg (88%) yellow powder.

Anal. calc. for C₅₂H₉₄N₄O₆S₂(935.46 g mol^-1) C 66.76, H 10.13, N

5.99, S 6.86%; found C 66.79, H 10.19, N 5.59, S 5.41%. ¹H NMR

3

(300 MHz, DMSO-d₆) d = 0.93 (t, 24H, J_HH= 7.3 Hz, C4_C-H),

3

1.30 (psext, 16H, J_HH= 7.4 Hz, C3_C-H), 1.52–1.62 (m, 16H,

C2_C-H), 1.96 (s, 6H, C2_A-H), 1.97 (s, 12H, C7_A-H), 3.14–3.20

(m, 16H, C1_C-H), 7.33 (s, 4H, C5_A-H) ppm; ¹³C NMR (75 MHz,

DMSO-d₆) d = 13.4 (C4_C), 15.6 (C2_A), 17.3 (C7_A), 19.2 (C3_C),

23.0 (C2_C), 57.5 (C1_C), 123.1 (C4_A), 125.2 (C5_A), 143.5 (C6_A),

147.9 (C3_A), 167.7 (C1_A) ppm. MS (ESI+) m/z (%) = 242.2829

(100, C₁₆H₃₆N requires 242.2842, [cation]⁺); MS (ESI-) m/z (%) =

225.0455 (100, C₂₀H₂₂N₂O₆S₂requires 225.0465, [anion]^2-), 693

(12, [anion + cation]^-). IR (neat) n = 2958 (m), 2873 (w), 1634 (w),

1488 (w), 1463 (m), 1380 (w), 1364 (w), 1235 (w), 1212 (m), 1185

(s), 1123 (w), 1105 (m), 1033 (s), 883 (m), 714 (w), 646 (s), 627 (s),

606 (w), 586 (w), 552 (w), 521 (w), 496 (w) cm^-1.

Bis(1-n-butyl-2,3-dimethylimidazolium) N,N¢-bis(2,6-diisoprop-

yl-4-sulfonatophenyl)butane-2,3-diimine (8c) [BMMIM]₂[2,6-iPr₂-

Me-DAD^S]. Prepared from 4c (1.03 g, 1.34 mmol, 1.00 eq) and

1-n-butyl-2-methylidene-3-methylimidazoline (0.49 g, 3.20 mmol,

2.39 eq): 0.80 g (69%) yellow powder. ¹H NMR (300 MHz, DMSO-

3

d₆) d = 0.90 (t, 6H, J_HH= 7.3 Hz, C9_C-H), 1.09 (d, 12H, J_HH

=

6.8 Hz, C8a_A-H), 1.15 (d, 12H, ³J_HH= 6.8 Hz, C8b_A-H), 1.28 (psext,

4H, J_HH= 7.6 Hz, C8_C-H), 1.68 (pquint, 4H, J_HH= 7.4 Hz,

3

C7_C-H), 1.99 (s, 6H, C2_A-H), 2.58 (s, 6H, C10_C-H), 2.66 (sept,

3

Bis(N,N,N¢,N¢,N¢¢-penta-n-butyl-N¢¢-methylguanidinium) N,

4H, J_HH= 6.8 Hz, C7_A-H), 3.74 (s, 6H, C11_C-H), 4.10 (t, 4H,

3

N¢-bis(2,6-dimethyl-4-sulfonatophenyl)butane-2,3-diimine

(11)

³J_HH= 7.3 Hz, C6_C-H), 7.41 (s, 4H, C5_A-H), 7.62 (d, 2H, J_HH

=

[Gua-4,4-4,4-4,1]₂[2,6-Me₂-Me-DAD^S]. Prepared

from

4a

1.9 Hz, C4_C-H), 7.65 (d, 2H, J_HH= 2.0 Hz, C5_C-H) ppm; ¹³C

NMR (75 MHz, DMSO-d₆) d = 9.1 (C10_C), 13.3 (C9_C), 16.3 (C2_A),

18.8 (C8_C), 22.3 (C8a_A), 22.7 (C8b_A), 28.0 (C7_A), 31.1 (C7_C), 34.6

(C11_C), 47.2 (C6_C), 120.4 (C5_A), 120.8 (C5_C), 122.3 (C4_C), 133.5

(C4_A), 144.0 (C6_A), 144.2 (C2_C), 145.7 (C3_A), 168.0 (C1_A) ppm.

MS (ESI+) m/z (%) = 153.1385 (100, C₉H₁₇N₂requires 153.1386,

[cation]⁺); MS (ESI-) m/z (%) = 281.1085 (100, C₂₈H₃₈N₂O₆S₂

requires 281.1091, [anion]^2-), 563 (4, [anion + H]^-), 715.3451 (8,

C₃₇H₅₅N₄O₆S₂requires 715.3569, [anion + cation]^-). IR (neat) n =

3091 (w), 2964 (w), 1650 (w), 1590 (w), 1541 (w), 1463 (w), 1436

(w), 1419 (w), 1362 (w), 1261 (w), 1196 (vs), 1152 (w), 1137 (w),

1120 (m), 1099 (w), 1072 (m), 1034 (s), 940 (w), 885 (w), 850 (w),

795 (w), 760 (m), 731 (w), 669 (w), 648 (m), 635 (s), 617 (m), 553

(w), 539 (w), 510 (w), 443 (w) cm^-1.

3

(199 mg, 0.30 mmol, 1.00 eq) and N,N,N¢,N¢,N¢¢-penta-

n-butyl-N¢¢-methylguanidinium methylcarbonate (259 mg,

0.60 mmol, 2.01 eq): 342 mg (98%) yellow powder. Anal. calc.

for C₆₄H₁₁₈N₈O₆S₂(1159.80 g mol^-1) C 66.28, H 10.25, N 9.66,

1

S 5.53%; found C 65.92, H 10.11, N 9.58, S 5.15%. H NMR

(300 MHz, DMSO-d₆) d = 0.86–0.92 (m, 30H, C4a-e_C-H),

1.17–1.72 (m, 40H, C3a-e_C-H and C2a-e_C-H), 1.96 (s, 6H,

C2_A-H), 1.97 (s, 12H, C7_A-H), 2.87 (s, 6H, C1f_C-H), 2.91–3.30 (m,

20H, C1a-e_C-H), 7.32 (s, 4H, C5_A-H) ppm; ¹³C NMR (75 MHz,

DMSO-d₆) d = 13.46 (C4a-d_C), 13.51 (C4e_C), 15.6 (C2_A), 17.3

(C7_A), 19.3, 19.4, 19.5 (C3a-e_C), 28.6, 28.7, 28.8, 29.0, 29.2

(C2a-e_C), 37.6 (C1f_C), 48.2, 48.5, 48.6, 49.0 (C1a-d_C), 51.9 (C1e_C),

123.1 (C4_A), 125.2 (C5_A), 143.5 (C6_A), 147.9 (C3_A), 163.2 (C_Gua),

12736 | Dalton Trans., 2011, 40, 12727–12741

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Palladium complexes

[PdCl₂(MeCN)₂] (36 mg, 0.14 mmol, 1.08 eq): 115 mg (88%) light

brown powder. ¹H NMR (300 MHz, DMSO-d₆) d = 0.90 (t, 6H,

General procedure for the preparation of complexes of the type

[BMMIM]₂[PdCl₂(DAD^S)] (12a–d). A mixture of the appropri-

ate DAD^Sligand 8 (0.1–0.2 mmol, 1.0 eq) and [PdCl₂(MeCN)₂]

(1.1 eq) was stirred in acetonitrile (10–20 mL) at room temperature

overnight. After removal of all volatiles in vacuo the crude product

was washed with ether and dried at 10^-2mbar.

3

³J_HH= 7.3 Hz, C9_C-H), 1.19 (d, 12H, J_HH= 6.8 Hz, C8a_A-H),

3

1.27 (psext, 4H, J_HH= 7.6 Hz, C8_C-H), 1.36 (d, 12H, J_HH

=

3

6.7 Hz, C8b_A-H), 1.67 (pquint, 4H, J_HH= 7.4 Hz, C7_C-H), 2.22

3

(s, 6H, C2_A-H), 2.57 (s, 6H, C10_C-H), 3.20 (sept, 4H, J_HH

=

6.8 Hz, C7_A-H), 3.73 (s, 6H, C11_C-H), 4.10 (t, 4H, ³J_HH= 7.3 Hz,

C6_C-H), 7.45 (s, 4H, C5_A-H), 7.61 (d, 2H, ³J_HH= 2.1 Hz, C4_C-H),

7.64 (d, 2H, J_HH= 2.1 Hz, C5_C-H) ppm; ¹³C NMR (75 MHz,

3

Bis(1-n-butyl-2,3-dimethylimidazolium) {N,N¢-bis(2,6-dimeth-

yl-4-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}dichloropalladi-

um(II) (12a) [BMMIM]₂[PdCl₂(2,6-Me₂-Me-DAD^S)]. Prepared

from 8a (155 mg, 0.20 mmol, 1.00 eq) and [PdCl₂(MeCN)₂] (56 mg,

0.21 mmol, 1.05 eq): 187 mg (98%) light orange powder. ¹H NMR

(300 MHz, DMSO-d₆) d = 0.90 (t, 6H, ³J_HH= 7.3 Hz, C9_C-H), 1.27

(psext, 4H, ³J_HH= 7.5 Hz, C8_C-H), 1.67 (pquint, 4H, ³J_HH= 7.5 Hz,

C7_C-H), 2.07 (s, 6H, C2_A-H), 2.26 (s, 12H, C7_A-H), 2.57 (s, 6H,

C10_C-H), 3.74 (s, 6H, C11_C-H), 4.10 (t, 4H, ³J_HH= 7.3 Hz, C6_C-H),

7.33 (s, 4H, C5_A-H), 7.62 (d, 2H, ³J_HH= 2.1 Hz, C4_C-H), 7.65 (d,

2H, ³J_HH= 2.1 Hz, C5_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆):

d = 9.1 (C10_C), 13.4 (C9_C), 17.8 (C7_A), 18.8 (C8_C), 19.7 (C2_A),

31.1 (C7_C), 34.6 (C11_C), 47.2 (C6_C), 120.8 (C5_C), 122.3 (C4_C),

125.0 (C5_A), 128.7 (C4_A), 143.0 (C6_A), 144.2 (C2_C), 146.9 (C3_A),

181.8 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1384 (100, C₉H₁₇N₂

requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) = 225 (34, [anion

- PdCl₂]^2-), 451 (29, [anion - PdCl₂+ H]^-), 557 (35, [anion - H -

2Cl]^-), 595 (22, [anion - Cl]^-), 628.9428 (100, C₂₀H₂₃Cl₂N₂O₆PdS₂

requires 628.9406, [anion + H]^-). IR (neat) n = 3099 (w), 2958 (w),

1587 (w), 1538 (w), 1463 (w), 1381 (w), 1237 (m), 1195 (vs), 1146

(m), 1106 (m), 1039 (vs), 1015 (m), 878 (w), 755 (w), 668 (w), 649

(s), 632 (vs), 619 (s), 555 (m), 525 (w), 456 (w) cm^-1.

DMSO-d₆) d = 9.1 (C10_C), 13.3 (C9_C), 18.8 (C8_C), 20.7 (C2_A),

23.3 (C8a_A), 23.5 (C8b_A), 28.2 (C7_A), 31.1 (C7_C), 34.6 (C11_C),

47.2 (C6_C), 120.7 (C5_A), 120.8 (C5_C), 122.3 (C4_C), 138.7 (C4_A),

140.3 (C6_A), 144.2 (C2_C), 147.9 (C3_A), 181.9 (C1_A) ppm. MS

(ESI+) m/z (%) = 153.1385 (100, C₉H₁₇N₂requires 153.1386,

[cation]⁺); MS (ESI-) m/z (%) = 370 (100, [anion]^2-), 891.1975

(15, C₃₇H₅₅Cl₂N₄O₆PdS₂requires 891.1980, [anion + cation]^-),

1043.3268 (2, C₄₆H₇₁Cl₂N₆O₆PdS₂requires 1043.3294, [anion +

2 ¥ cation - H]^-). IR (neat) n = 2959 (w), 2929 (w), 2869 (w), 1586

(w), 1537 (w), 1462 (w), 1416 (w), 1382 (w), 1193 (s), 1070 (m),

1032 (s), 1012 (m), 885 (w), 748 (w), 657 (w), 635 (vs), 539 (w),

523 (w) cm^-1.

Bis(triethylammonium)

{N,N¢-bis(2,6-dimethyl-4-sulfonato-

phenyl)butane-2,3-diimine-j²N,N¢}dichloropalladium(II)

(12d)

4a

[HNEt₃]₂[PdCl₂(2,6-Me₂-Me-DAD^S)].

A

mixture

of

(213 mg, 0.33 mmol, 1.00 eq) and [PdCl₂(MeCN)₂] (89 mg,

0.34 mmol, 1.05 eq) was stirred in acetonitrile (30 mL) at

room temperature overnight. The precipitated product was

isolated by centrifugation, washed with hexane and dried at

10^-2mbar. The mother liquor was used for the preparation of

single crystals. Yield: 120 mg (44%) yellow powder. Anal. calc.

for C₃₂H₅₄Cl₂N₄O₆PdS₂(832.25 g mol^-1) C 46.18, H 6.54, N

6.73, S 7.71%; found C 45.32, H 6.38, N 6.50, S 7.51%. ¹H

Bis(1-n-butyl-2,3-dimethylimidazolium) {N,N¢-bis(2,4,6-trime-

thyl-3-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}dichloropalla-

dium(II) (12b) [BMMIM]₂[PdCl₂(2,4,6-Me₃-Me-DAD^S)]. Pre-

pared from 8b (106 mg, 0.14 mmol, 1.00 eq) and [PdCl₂(MeCN)₂]

3

NMR (300 MHz, DMSO-d₆) d = 1.17 (t, 18H, J_HH= 7.3 Hz,

C2_C-H), 2.08 (s, 6H, C2_A-H), 2.27 (s, 12H, C7_A-H), 3.08 (dq,

12H, ³J_HH= 4.9, 7.2 Hz, C1_C-H), 7.35 (s, 4H, C5_A-H), 8.91 (br s,

2H, NH⁺) ppm; ¹³C NMR (75 MHz, DMSO-d₆): d = 8.6 (C2_C),

17.8 (C7_A), 19.7 (C2_A), 45.8 (C1_C), 125.0 (C5_A), 128.8 (C4_A),

143.1 (C6_A), 146.7 (C3_A), 181.7 (C1_A) ppm. MS (ESI+) m/z (%) =

102.1279 (100, C₆H₁₆N requires 102.1277, [cation]⁺); MS (ESI-)

m/z (%) = 225 (18, [anion - PdCl₂]^2-), 314 (100, [anion]^2-), 451 (7,

[anion - PdCl₂+ H]^-), 629 (34, [anion + H]^-). IR (neat) n = 2983

(br w), 2698 (br w), 2504 (w), 1457 (w), 1401 (w), 1382 (w), 1217

(m), 1167 (m), 1107 (m), 1037 (s), 1018 (m), 880 (w), 834 (w), 791

(w), 651 (s), 634 (s), 619 (m), 556 (w), 526 (w), 446 (w) cm^-1.

1

(39 mg, 0.15 mmol, 1.11 eq): 115 mg (89%) orange powder. H

NMR (300 MHz, DMSO-d₆) d = 0.89 (t, 6H, ³J_HH= 7.3 Hz, C9_C-

3

H), 1.26 (psext, 4H, J_HH= 7.5 Hz, C8_C-H), 1.67 (pquint, 4H,

³J_HH= 7.5 Hz, C7_C-H), 2.03 (s, 6H, C2_A-H), 2.20, 2.50, 2.51 (3 ¥ s,

3 ¥ 6H, C2_A-H and C9-11_A-H), 2.56 (s, 6H, C10_C-H), 3.73 (s, 6H,

C11_C-H), 4.09 (t, 4H, ³J_HH= 7.3 Hz, C6_C-H), 6.88 (s, 2H, C7_A-H),

3

7.61 (d, 2H, J_HH= 1.9 Hz, C4_C-H), 7.64 (d, 2H, J_HH= 1.9 Hz,

C5_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆) d = 9.1 (C10_C),

13.4 (C9_C), 16.3 (C9_A), 17.8 (C11_A), 18.8 (C8_C), 19.5 (C2_A), 22.9

(C10_A), 31.1 (C7_C), 34.6 (C11_C), 47.2 (C6_C), 120.8 (C5_C), 122.3

(C4_C), 127.8, 128.4 (C4_Aand C8_A), 130.5 (C7_A), 135.0 (C6_A), 141.9

(C5_A), 144.0 (C3_A), 144.2 (C2_C), 181.5 (C1_A) ppm. MS (ESI+) m/z

(%) = 153.1384 (100, C₉H₁₇N₂requires 153.1386, [cation]⁺); MS

(ESI-) m/z (%) = 238 (10, [anion - PdCl₂]^2-), 479 (26, [anion -

PdCl₂+ H]^-), 583 (100, [anion - H - 2Cl]^-), 656.9748 (44,

C₂₂H₂₇Cl₂N₂O₆PdS₂requires 656.9718, [anion + H]^-). IR (neat)

n = 2958 (w), 2928 (w), 2871 (w), 1586 (w), 1537 (w), 1450 (w),

1420 (w), 1377 (w), 1192 (br vs), 1136 (m), 1052 (s), 1019 (m), 985

(m), 872 (w), 750 (w), 706 (w), 687 (m), 664 (m), 634 (s), 578 (w),

558 (m), 542 (m), 523 (m) cm^-1.

Platinum complexes

General procedure for the preparation of complexes of the

type [BMMIM]₂[PtCl₂(DAD^S)] (13a–c). A mixture of the ap-

propriate DAD^Sligand 8 (0.1 mmol, 1.0 eq) and Zeise’s dimer,

[{PtCl₂(C₂H₄)}₂], (0.05 mmol, 0.5 eq) was stirred in methanol

(10 mL) for three days at room temperature. After removal of

all volatiles in vacuo the crude product was washed with ether and

dried at 10^-2mbar.

Bis(1-n-butyl-2,3-dimethylimidazolium)

{N,N¢-bis(2,6-diiso-

Bis(1-n-butyl-2,3-dimethylimidazolium) {N,N¢-bis(2,6-dimeth-

yl-4-sulfonatophenyl)butane-2,3-diimine-j²N ,N¢}dichloroplati-

num(II) (13a) [BMMIM]₂[PtCl₂(2,6-Me₂-Me-DAD^S)]. Prepared

from 8a (76 mg, 0.10 mmol, 1.00 eq) and Zeise’s dimer (29 mg,

propyl-4-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}dichloropa-

lladium(II)

(12c)

[BMMIM]₂[PdCl₂(2,6-iPr₂-Me-DAD^S)].

Prepared from 8c (109 mg, 0.13 mmol, 1.00 eq) and

This journal is The Royal Society of Chemistry 2011

Dalton Trans., 2011, 40, 12727–12741 | 12737

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0.05 mmol, 0.50 eq): 93 mg (91%) dark orange powder. Anal.

calc. for C₃₈H₅₆Cl₂N₆O₆PtS₂(1023.00 g mol^-1) C 44.61, H 5.52,

(s, 4H, C5_A-H), 7.61 (d, 2H, ³J_HH= 2.1 Hz, C4_C-H), 7.65 (d, 2H,

³J_HH= 2.1 Hz, C5_C-H) ppm; ¹³C NMR (75 MHz, DMSO-d₆)

d = 9.1 (C10_C), 13.3 (C9_C), 18.8 (C8_C), 20.4 (C2_A), 23.2 (C8a_A),

23.5 (C8b_A), 27.6 (C7_A), 31.1 (C7_C), 34.6 (C11_C), 47.2 (C6_C),

120.7 (C5_A), 120.8 (C5_C), 122.3 (C4_C), 139.4 (C4_A), 140.4 (C6_A),

144.2 (C2_C), 148.2 (C3_A), 180.9 (C1_A) ppm; ¹⁹⁵Pt NMR (86 MHz,

DMSO-d₆) d = -2169 ppm. MS (ESI+) m/z (%) = 153.1385

(100, C₉H₁₇N₂requires 153.1386, [cation]⁺); MS (ESI-) m/z

(%) = 415 (100, [anion]^2-), 829 (16, [anion + H]^-), 980.2534 (10,

C₃₇H₅₅Cl₂N₄O₆PtS₂requires 980.2593, [anion + cation]^-). IR

(neat) n = 2958 (w), 2929 (w), 2868 (w), 1586 (w), 1537 (w), 1462

(w), 1418 (w), 1385 (w), 1363 (w), 1332 (w), 1193 (br s), 1070 (m),

1033 (s), 1014 (m), 943 (w), 886 (w), 830 (w), 750 (w), 652 (w),

636 (vs), 565 (w), 539 (w), 524 (w), 480 (w) cm^-1.

1

N 8.22, S 6.27%; found C 44.90, H 5.71, N 8.29, S 6.03%. H

3

NMR (300 MHz, DMSO-d₆) d = 0.90 (t, 6H, J_HH= 7.3 Hz,

3

C9_C-H), 1.27 (psext, 4H, J_HH= 7.6 Hz, C8_C-H), 1.68 (pquint,

3

4H, J_HH= 7.4 Hz, C7_C-H), 1.76 (s, 6H, C2_A-H), 2.22 (s, 12H,

C7_A-H), 2.57 (s, 6H, C10_C-H), 3.74 (s, 6H, C11_C-H), 4.10 (t, 4H,

3

³J_HH= 7.3 Hz, C6_C-H), 7.39 (s, 4H, C5_A-H), 7.62 (d, 2H, J_HH

=

2.0 Hz, C4_C-H), 7.65 (d, 2H, ³J_HH= 2.0 Hz, C5_C-H) ppm; ¹³C NMR

(75 MHz, DMSO-d₆) d = 9.1 (C10_C), 13.4 (C9_C), 17.2 (C7_A), 18.8

(C8_C), 19.3 (C2_A), 31.1 (C7_C), 34.6 (C11_C), 47.2 (C6_C), 120.8 (C5_C),

122.3 (C4_C), 125.0 (C5_A), 129.4 (C4_A), 143.1 (C6_A), 144.2 (C2_C),

147.3 (C3_A), 180.1 (C1_A) ppm; ¹⁹⁵Pt NMR (86 MHz, DMSO-d₆)

d = -2193 ppm. MS (ESI+) m/z (%) = 153.1386 (100, C₉H₁₇N₂

requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) = 357.4969

(100, C₂₀H₂₂Cl₂N₂O₆PtS₂requires 357.4978, [anion]^2-), 868.1328

(18, C₂₉H₃₉Cl₂N₄O₆PtS₂requires 868.1341, [anion + cation]^-). IR

(neat) n = 2957 (w), 2871 (w), 1587 (w), 1537 (w), 1458 (br w),

1383 (w), 1237 (w), 1192 (br s), 1105 (m), 1037 (s), 880 (w), 754

(w), 722 (w), 668 (m), 632 (vs), 618 (m), 556 (w), 525 (w), 461 (w),

443 (w) cm^-1.

Rhodium complexes

General procedure for the preparation of complexes of the

type [BMMIM][Rh(COD)(DAD^S)] (14a–c). A mixture of silver

tetraﬂuoroborate (0.1–0.2 mmol, 1.0 eq) and [{RhCl(COD)}₂]

(0.05–0.1 mmol, 0.5 eq) was stirred in acetonitrile (10 mL) for one

hour at room temperature. The precipitated silver chloride was

removed using a syringe ﬁlter (PTFE, 0.45 mm) and the solution

was added to a suspension of the appropriate DAD^Sligand 8

(0.1–0.2 mmol, 1.0 eq) in acetonitrile (20 mL). The reaction

mixture was then stirred for one hour at room temperature. After

removal of all volatiles in vacuo the crude product was treated

with dichloromethane–ether (1 : 1, 5–10 mL each). The desired

complex was isolated by ﬁltration, washed with ether and dried at

10^-2mbar.

Bis(1-n-butyl-2,3-dimethylimidazolium) {N,N¢-bis(2,4,6-trime-

thyl-3-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}dichloroplati-

num(II) (13b) [BMMIM]₂[PtCl₂(2,4,6-Me₃-Me-DAD^S)]. Pre-

pared from 8b (79 mg, 0.10 mmol, 1.00 eq) and Zeise’s dimer

(29 mg, 0.05 mmol, 0.50 eq): 100 mg (95%) dark orange powder.

Anal. calc. for C₄₀H₆₀Cl₂N₆O₆PtS₂(1051.06 g mol^-1) C 45.71, H

5.75, N 8.00, S 6.10%; found C 44.71, H 5.76, N 7.84, S 5.46%.

3

¹H NMR (300 MHz, DMSO-d₆) d = 0.90 (t, 6H, J_HH= 7.3 Hz,

C9_C-H), 1.27 (psext, 4H, ³J_HH= 7.6 Hz, C8_C-H), 1.67 (pquint, 4H,

³J_HH= 7.5 Hz, C7_C-H), 1.71 (s, 6H, C2_A-H), 2.16, 2.46, 2.56 (3 ¥ s, 3

¥ 6H, C9-11_A-H), 2.57 (s, 6H, C10_C-H), 3.74 (s, 6H, C11_C-H), 4.10

1-n-Butyl-2,3-dimethylimidazolium {N,N¢-bis(2,6-dimethyl-4-

sulfonatophenyl)butane-2,3-diimine-j²N,N¢}{g²:g²-(Z,Z)-cyclo-

octa-1,5-diene}rhodium(I) (14a) [BMMIM][Rh(COD)(2,6-Me₂-

Me-DAD^S)]. Prepared from AgBF₄(29 mg, 0.15 mmol, 1.03 eq),

[{RhCl(COD)}₂] (36 mg, 0.07 mmol, 0.51 eq) and 8a (109 mg,

3

(t, 4H, J_HH= 7.3 Hz, C6_C-H), 6.94 (s, 2H, C7_A-H), 7.62 (d, 2H,

³J_HH= 2.0 Hz, C4_C-H), 7.65 (d, 2H, ³J_HH= 2.0 Hz, C5_C-H) ppm;

¹³C NMR (75 MHz, DMSO-d₆) d = 9.1 (C10_C), 13.4 (C9_C), 15.6

(C9_A), 17.2 (C11_A), 18.8 (C8_C), 19.1 (C2_A), 22.9 (C10_A), 31.1 (C7_C),

34.6 (C11_C), 47.2 (C6_C), 120.8 (C5_C), 122.3 (C4_C), 128.6, 129.0

(C4_Aand C8_A) 130.5 (C7_A), 135.3 (C6_A), 142.0 (C5_A), 144.0 (C3_A),

144.2 (C2_C), 180.3 (C1_A) ppm; ¹⁹⁵Pt NMR (86 MHz, DMSO-d₆)

d = -2192 ppm. MS (ESI+) m/z (%) = 153.1388 (100, C₉H₁₇N₂

requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) = 371.5128

(100, C₂₂H₂₆Cl₂N₂O₆PtS₂requires 371.5134, [anion]^2-), 896.1613

(22, C₃₁H₄₃Cl₂N₄O₆PtS₂requires 896.1654, [anion + cation]^-). IR

(neat) n = 2957 (w), 2930 (w), 2871 (w), 1587 (w), 1537 (w), 1452

(w), 1379 (w), 1338 (w), 1192 (br vs), 1136 (m), 1053 (s), 1020 (m),

986 (m), 863 (w), 751 (w), 708 (m), 691 (m), 666 (m), 640 (s), 613

(m), 578 (m), 558 (m), 544 (m), 523 (m) cm^-1.

1

0.14 mmol, 1.00 eq): 67 mg (57%) olive-green powder. H NMR

3

(500 MHz, DMSO-d₆) d = 0.90 (t, 3H, J_HH= 7.4 Hz, C9_C-H),

1.28 (psext, 2H, ³J_HH= 7.5 Hz, C8_C-H), 1.68 (pquint, 2H, ³J_HH

=

7.4 Hz, C7_C-H), 1.82–1.88 (m, 4H, Cb_A-Ha), 2.12 (s, 6H, C2_A-H),

2.27–2.34 (m, 4H, Cb_A-Hb), 2.33 (s, 12H, C7_A-H), 2.58 (s, 3H,

C10_C-H), 3.44 (br s, 4H, Ca_A-H), 3.74 (s, 3H, C11_C-H), 4.10 (t,

3

2H, J_HH= 7.4 Hz, C6_C-H), 7.44 (s, 4H, C5_A-H), 7.61 (d, 1H,

³J_HH= 2.1 Hz, C4_C-H), 7.65 (d, 1H, ³J_HH= 2.1 Hz, C5_C-H) ppm;

¹³C NMR (126 MHz, DMSO-d₆) d = 9.1 (C10_C), 13.4 (C9_C),

17.5 (C7_A), 18.8 (C8_C), 19.3 (C2_A), 29.8 (Cb_A), 31.1 (C7_C), 34.6

1

(C11_C), 47.2 (C6_C), 89.2 (d, J_RhC= 11.5 Hz, Ca_A), 120.8 (C5_C),

122.3 (C4_C), 125.7 (C5_A), 127.7 (C4_A), 141.2 (C6_A), 144.2 (C2_C),

147.2 (C3_A), 181.7 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1385

(100, C₉H₁₇N₂requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) =

225 (23, [anion - Rh(COD)]^2-), 661.0899 (100, C₂₈H₃₄N₂O₆RhS₂

requires 661.0919, [anion]^-). IR (neat) n = 2956 (w), 1466 (w), 1430

(w), 1380 (w), 1237 (w), 1216 (s), 1195 (vs), 1151 (w), 1109 (m),

1038 (s), 1010 (m), 994 (m), 968 (m), 880 (w), 650 (s), 633 (s), 619

(s), 555 (w), 524 (w), 429 (w) cm^-1.

Bis(1-n-butyl-2,3-dimethylimidazolium)

{N,N¢-bis(2,6-diiso-

propyl-4-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}dichloropla-

tinum(II)

(13c)

[BMMIM]₂[PtCl₂(2,6-iPr₂-Me-DAD^S)].

Prepared from 8c (78 mg, 0.09 mmol, 1.00 eq) and Zeise’s

dimer (28 mg, 0.05 mmol, 0.50 eq): 83 mg (81%) brown powder.

3

¹H NMR (300 MHz, DMSO-d₆) d = 0.90 (t, 6H, J_HH= 7.3 Hz,

3

C9_C-H), 1.17 (d, 12H, J_HH= 6.8 Hz, C8a_A-H), 1.27 (psext, 4H,

3

³J_HH= 7.6 Hz, C8_C-H), 1.31 (d, 12H, J_HH= 6.7 Hz, C8b_A-H),

1-n-Butyl-2,3-dimethylimidazolium {N,N¢-bis(2,4,6-trimethyl-

3 - sulfonatophenyl ) butane - 2,3 - diimine - j²N,N¢ }{g²:g²- ( Z,Z )-

cycloocta-1,5-diene}rhodium(I) (14b) [BMMIM][Rh(COD)(2,4,6-

Me₃-Me-DAD^S)]. Prepared from AgBF₄(32 mg, 0.16 mmol,

3

1.67 (pquint, 4H, J_HH= 7.5 Hz, C7_C-H), 1.87 (s, 6H, C2_A-H),

3

2.57 (s, 6H, C10_C-H), 3.11 (sept, 4H, J_HH= 6.8 Hz, C7_A-H),

3

3.73 (s, 6H, C11_C-H), 4.10 (t, 4H, J_HH= 7.3 Hz, C6_C-H), 7.50

12738 | Dalton Trans., 2011, 40, 12727–12741

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◦

was treated with toluene (60 mL) and heated to 95 C for 20 h.

1.08 eq), [{RhCl(COD)}₂] (38 mg, 0.08 mmol, 0.51 eq) and 8b

The resulting solution was evaporated to dryness. The almost

black crude product was recrystallized from toluene and dried in

vacuo, yielding 1351 mg (77%) violet crystals with a strong green

luster. Anal. calc. for C₂₄H₂₄MoN₂O₄(500.40 g mol^-1) C 57.61,

(119 mg, 0.15 mmol, 1.00 eq): 105 mg (83%) greenish-brown

powder. ¹H NMR (500 MHz, DMSO-d₆) d = 0.90 (t, 3H, ³J_HH

=

3

7.4 Hz, C9_C-H), 1.28 (psext, 2H, J_HH= 7.6 Hz, C8_C-H), 1.68

3

(pquint, 2H, J_HH= 7.5 Hz, C7_C-H), 1.77–1.91 (m, 4H, Cb_A-

1

H 4.83, N 5.60%; found C 57.54, H 4.83, N 5.59%. H NMR

Ha), 2.10 (s, 6H, C2_A-H), 2.21–2.30 (m, 4H, Cb_A-Hb), 2.27, 2.28

(2 ¥ s, 6H, C11_A-H, conformers), 2.54 (s, 6H, C10_A-H), 2.56 (s,

(300 MHz, CD₃CN) d = 2.08 (s, 6H, C2-H), 2.23 (s, 12H, C7-H),

7.11–7.23 (m, 6H, C5-H and C6-H) ppm; ¹³C NMR (75 MHz,

CD₃CN) d = 18.5 (C7), 19.9 (C2), 126.9 (C6), 128.2 (C4), 129.8

(C5), 149.8 (C3), 172.8 (C1), 206.8 (CO_trans), 223.5 (CO_cis) ppm.

MS (ESI+) m/z (%) = 475.0915 (24, C₂₃H₂₅MoN₂O₃requires

475.0916, [M - CO + H]⁺), 497 (100, [M - CO + Na]⁺), 525.0684

(18, C₂₄H₂₄MoN₂NaO₄requires 525.0687, [M + Na]⁺), 1024.1500

(20, C₄₈H₄₈Mo₂N₄NaO₈requires 1024.1494, [2M + Na]⁺). IR

(neat) n = 2926 (w), 1993 (s), 1904 (w), 1891 (w), 1847 (br vs),

1588 (w), 1505 (w), 1461 (w), 1440 (w), 1377 (m), 1317 (m), 1217

(m), 1093 (w), 981 (m), 850 (w), 766 (m), 701 (w), 633 (m), 618

(w), 580 (m), 536 (m), 522 (w), 436 (w), 416 (w) cm^-1.

6H, C9_A-H), 2.58 (s, 3H, C10_C-H), 3.32 (br s, 2H, Ca_A-H), 3.51

3

(br s, 2H, Ca¢_A-H), 3.74 (s, 3H, C11_C-H), 4.10 (t, 2H, J_HH

=

7.3 Hz, C6_C-H), 7.01 (s, 2H, C7_A-H), 7.61 (d, 1H, ³J_HH= 2.0 Hz,

C4_C-H), 7.65 (d, 1H, J_HH= 2.0 Hz, C5_C-H) ppm; ¹³C NMR

3

(100 MHz, DMSO-d₆) d = 9.1 (C10_C), 13.4 (C9_C), 16.2, 16.3 (C9_A,

conformers), 17.49, 17.53 (C11_A, conformers), 18.9 (C8_C), 19.2

(C2_A), 22.8 (C10_A), 29.4, 29.8, 30.2 (Cb_Aand Cb¢_A, conformers),

1

31.2 (C7_C), 34.6 (C11_C), 47.3 (C6_C), 88.7 (d, J_RhC= 11.7 Hz,

1

Ca_A), 89.2 (d, J_RhC= 11.7 Hz, Ca¢_A), 120.9 (C5_C), 122.3 (C4_C),

126.6, 126.7 (C4_A, conformers), 127.2, 127.3 (C8_A, conformers),

131.3 (C7_A), 134.9 (C6_A), 140.0 (C5_A), 144.2 (C2_C), 144.6 (C3_A),

181.6 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1385 (100, C₉H₁₇N₂

requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) = 239 (7, [anion -

Rh(COD)]^2-), 689.1202 (100, C₃₀H₃₈N₂O₆RhS₂requires 689.1232,

[anion]^-). IR (neat) n = 2958 (w), 2928 (w), 1536 (w), 1450 (w),

1379 (w), 1243 (w), 1198 (vs), 1053 (s), 1020 (m), 993 (m), 848 (w),

773 (w), 751 (w), 707 (m), 686 (m), 663 (s), 631 (s), 577 (w), 558

(m), 541 (m), 523 (m) cm^-1.

Preparation of bis(1-n-butyl-2,3-dimethylimidazolium) {N,N¢-

bis(2,6-dimethyl-4-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}-

tetracarbonylmolybdenum(0) (16) [BMMIM]₂[Mo(CO)₄(2,6-Me₂-

Me-DAD^S)]. A mixture of 8a (1156 mg, 1.53 mmol, 1.00 eq)

and molybdenum hexacarbonyl (438 mg, 1.65 mmol, 1.08 eq) was

treated with 1,2-dichloroethane (60 mL) and heated to reﬂux for

20 h. The resulting solution was evaporated to dryness. The dark

crude product was recrystallized from dichloromethane and dried

1-n-Butyl-2,3-dimethylimidazolium {N,N¢-bis(2,6-diisopropyl-

4-sulfonatophenyl)butane-2,3-diimine-j²N,N¢}{g²:g²-(Z,Z )-

cycloocta-1,5-diene}rhodium(I) (14c) [BMMIM][Rh(COD)(2,6-

iPr₂-Me-DAD^S)]. Prepared from AgBF₄(39 mg, 0.20 mmol,

1.02 eq), [{RhCl(COD)}₂] (49 mg, 0.10 mmol, 0.51 eq) and 8c

(170 mg, 0.20 mmol, 1.00 eq): 151 mg (57%) greenish-brown

1

in vacuo, yielding 1225 mg (83%) dark violet powder. H NMR

(300 MHz, CD₃CN) d = 0.93 (t, 6H, ³J_HH= 7.3 Hz, C9_C-H), 1.33

(psext, 4H, ³J_HH= 7.5 Hz, C8_C-H), 1.72 (pquint, 4H, ³J_HH= 7.2 Hz,

C7_C-H), 2.08 (s, 6H, C2_A-H), 2.23 (s, 12H, C7_A-H), 2.50 (s, 6H,

C10_C-H), 3.69 (s, 6H, C11_C-H), 4.03 (t, 4H, ³J_HH= 7.3 Hz, C6_C-H),

powder. ¹H NMR (500 MHz, DMSO-d₆) d = 0.90 (t, 3H, ³J_HH

=

7.30 (br s, 4H, C4_C-H and C5_C-H), 7.55 (s, 4H, C5_A-H) ppm; ¹³

C

7.4 Hz, C9_C-H), 1.17 (d, 12H, ³J_HH= 6.7 Hz, C8a_A-H), 1.28 (psext,

NMR (75 MHz, CD₃CN) d = 10.3 (C10_C), 13.8 (C9_C), 18.5 (C7_A),

20.0 (C2_A), 20.1 (C8_C), 32.3 (C7_C), 36.0 (C11_C), 49.0 (C6_C), 122.0

(C5_C), 123.5 (C4_C), 127.2 (C5_A), 127.8 (C4_A), 145.4 (C2_C), 147.0

(C6_A), 149.7 (C3_A), 173.0 (C1_A), 206.5 (CO_trans), 223.5 (CO_cis) ppm.

MS (ESI+) m/z (%) = 153.1386 (100, C₉H₁₇N₂requires 153.1386,

[cation]⁺); MS (ESI-) m/z (%) = 315 (44, [anion - CO]^2-), 329.9884

(100, C₂₄H₂₂MoN₂O₁₀S₂requires 329.9890, [anion]^2-), 813.1143

(25, C₃₃H₃₉MoN₄O₁₀S₂requires 813.1167, [anion + cation]^-). IR

(neat) n = 3103 (w), 2930 (w), 1996 (m), 1882 (s), 1855 (vs), 1588

(w), 1539 (w), 1500 (w), 1463 (w), 1379 (w), 1319 (w), 1274 (w),

1238 (w), 1197 (s), 1144 (m), 1108 (m), 1041 (s), 984 (m), 893 (w),

876 (w), 782 (w), 755 (w), 726 (w), 715 (w), 671 (w), 647 (s), 630

(vs), 615 (m), 579 (m), 557 (m), 522 (m), 462 (m), 428 (w) cm^-1.

3

2H, J_HH= 7.6 Hz, C8_C-H), 1.46 (d, 12H, J_HH= 6.8 Hz, C8b_A-

3

H), 1.68 (pquint, 2H, J_HH= 7.5 Hz, C7_C-H), 1.85–1.90 (m, 4H,

Cb_A-Ha), 2.18–2.24 (m, 4H, Cb_A-Hb), 2.34 (s, 6H, C2_A-H), 2.58

3

(s, 3H, C10_C-H), 3.28 (sept, 4H, J_HH= 6.7 Hz, C7_A-H), 3.53 (br

3

s, 4H, Ca_A-H), 3.75 (s, 3H, C11_C-H), 4.11 (t, 2H, J_HH= 7.3 Hz,

C6_C-H), 7.56 (s, 4H, C5_A-H), 7.62 (d, 1H, ³J_HH= 2.0 Hz, C4_C-H),

3

7.65 (d, 1H, J_HH= 2.0 Hz, C5_C-H) ppm; ¹³C NMR (126 MHz,

DMSO-d₆) d = 9.1 (C10_C), 13.4 (C9_C), 18.8 (C8_C), 21.3 (C2_A),

23.0 (C8b_A), 24.6 (C8a_A), 28.4 (C7_A), 29.4 (Cb_A), 31.1 (C7_C), 34.6

1

(C11_C), 47.2 (C6_C), 88.7 (d, J_RhC= 10.5 Hz, Ca_A), 120.8 (C5_C),

121.6 (C5_A), 122.3 (C4_C), 138.1, 138.4 (C4_Aand C6_A), 144.2 (C2_C),

148.3 (C3_A), 182.0 (C1_A) ppm. MS (ESI+) m/z (%) = 153.1386

(100, C₉H₁₇N₂requires 153.1386, [cation]⁺); MS (ESI-) m/z (%) =

282 (21, [anion - Rh(COD)]^2-), 773.2143 (100, C₃₆H₅₀N₂O₆RhS₂

requires 773.2171, [anion]^-). IR (neat) n = 2961 (w), 2929 (w), 2872

(w), 1463 (w), 1437 (w), 1381 (w), 1200 (s), 1152 (w), 1070 (m),

1034 (s), 1009 (m), 993 (w), 886 (w), 754 (w), 657 (w), 636 (s), 539

(w), 522 (w), 484 (w) cm^-1.

Single-crystal XRD studies

Crystallographic data are provided in Table 5 and full details

are available in ESI†. X-Ray data collection was performed via

a STOE IPDS I or IPDS II area detector using Mo-Ka-radiation

(l = 71.073 pm). STOE IPDS software⁴²was used for integration

and data reduction, structure solution and reﬁnement was done

with the WinGX program suite⁴³using SIR92⁴⁴and SHELX-

97.⁴⁵While the complex anion of 12d showed no unusual features

during the reﬁnement, both triethylammonium cations were found

to be poorly resolved due to their conformational ﬂexibility or

an irresolvable disorder. Bond lengths and 1,3-distances within

Molybdenum complexes

Preparation of {N,N¢-bis(2,6-dimethylphenyl)butane-2,3-dii-

mine-j²N,N¢}-tetracarbonylmolybdenum(0) (15) [Mo(CO)₄(2,6-

Me₂-Me-DAD)].

A

mixture

of

N,N¢-bis(2,6-dimethyl-

phenyl)butane-2,3-diimine (1019 mg, 3.48 mmol, 1.00 eq)

˚

and molybdenum hexacarbonyl (972 mg, 3.68 mmol, 1.06 eq)

the cations were ﬁxed to average target values (C–N 1.48 A,

This journal is

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Dalton Trans., 2011, 40, 12727–12741 | 12739

©

View Article Online

Table 5 Crystallographic data.

4a

6

8b

8c

12d

Chemical formula

M/g mol^-1

C₃₂H₅₄N₄O₆S₂

654.91

Monoclinic

C₃₆H₅₂N₆O₆S₂

728.96

C₄₀H₆₀N₆O₆S₂

785.08

C₄₆H₇₂N₆O₆S₂

869.22

Monoclinic

C₃₂H₅₄Cl₂N₄O₆PdS₂

832.21

Monoclinic

Crystal system

Triclinic

¯

Space group

P2₁/c

P1

P2₁/c

P2₁/a

˚

a/A

16.7780(14)

7.2899(9)

14.6759(11)

90.00

8.6734(10)

9.4661(12)

11.6547(13)

88.301(14)

88.487(14)

85.669(15)

953.46(19)

193(2)

7.4331(3)

8.3007(4)

17.9835(9)

86.492(4)

84.986(4)

65.819(3)

1007.96(8)

100(2)

18.7969(13)

8.4216(6)

14.6542(11)

90.00

13.5983(5)

7.4017(3)

38.4451(14)

90.00

˚

b/A

˚

c/A

a/^◦

b/^◦

g /^◦

101.533(9)

90.00

1758.8(3)

193(2)

93.811(6)

90.00

2314.6(3)

100(2)

90.841(3)

90.00

3869.1(3)

100(2)

3

˚

V/A

T/K

Z

2

1

2

4

No. reﬂections measured

No. independent reﬂections

R_int

13370

3200

0.0578

0.0375

8973

3378

0.0385

0.0389

8050

4158

0.0616

0.0446

12521

4879

0.1533

0.0493

22338

8201

0.1056

0.0677

Final R₁values (I > 2s(I))

Final wR(F²) values (all data)

0.0828

0.1080

0.1122

0.0785

0.1666

˚

C–C 1.45 A, N–C–C 2.45 A, C–N–C 2.49 A) while the thermal

movement was restrained to an approximately isotropic behaviour.

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Acknowledgements

Financial support by the DFG SPP 1191 (Ionic Liquids) and a

donation of precious metal halides by UMICORE AG are gratefully

acknowledged.

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Sulfonate-tagged 1,4-diazabutadiene (DADS) ligands and their noble-metal complexes - Synthesis, characterization and immobilization in ionic liquids

DOI: 10.1039/c1dt10939a

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